Application of Diodesgpambala.ac.in/wp-content/uploads/2018/04/Digital...Disadvantage of HWR The ripple factor of half wave rectifier is 1.21, which is quite high. •The output contains

Rectifiers

Application of Diodes

ContentsDesign of Rectifier Circuits.

Half Wave Rectification

Full Wave Rectifier

Filter

Ripple Voltage and Diode Current

Clippers.

Clampers.

Zener Diode Circuits

Zener Diode as Voltage Regulator

Block diagram of Power Supply

Half Wave Rectifier

Operation of Half Wave Rectifier

Waveform of Half Wave Rectifier

AC input power from transformer

secondary

How effectively a rectifier converts

ac into dc:

Ripple Factor (r)

Rectifier Efficiency (η)Tells us the percentage of total input ac

power that is convertedinto useful dc

output power.

η = 40.6 %

Under best conditions (no diode loss) only 40.6%

of the ac input power is converted into dc power.

The rest remains as the ac power in the load

Ripple Factor

Measure of purity of the dc output of a rectifier

Defined as the ratio of ac component of theoutput wave to the dc component in the wave

Ripple Factor

This indicates that the ripple content in the

output are 1.211 times the dc component.

i.e. 121.1 % of dc component.

The ripple factor is very high.

Therefore a half wave rectifier is a poor

converter of ac to dc.

The ripple factor is minimized using filter

circuits along with the rectifier.

Peak Inverse Voltage (PIV)

PIV = Em

Diode must be selected based on the PIV rating and

the circuit specification.

Disadvantage of HWR

The ripple factor of half wave rectifier is 1.21,

which is quite high.

•The output contains lot of ripples

•The maximum theoretical efficiency is 40%.

•The practical value will be quite less than this.

•This indicates that HWR is quite inefficient.

Center Tap Rectifier

Working of Center Tap Rectifier

Current Flow during the positive half of the input cycle

Current Flow during the negative half of the input cycle

Waveforms

1

DC Biasing Circuits

2

Objectives

• State the purpose of dc biasing circuits.

• Plot the dc load line given the value of VCC and the total collector-emitter circuit resistance.

• Describe the Q-point of an amplifier.

• Describe and analyze the operations of various bias circuits:

– base-bias circuits

– voltage-divider bias circuits

– emitter-bias circuits

– collector-feedback bias circuits

– emitter-feedback bias circuits

3

Fig 7.1 Typical amplifier operation.

RB

RC

Q1

VCC

VB(ac)

IB(ac)

VCE(ac)

IC(ac)

4

Fig 7.2 A generic dc load line.

IC

VCE

(sat)CC

C

C

VI

R

(off )CE CCV V

CC CEC

C

V VI

R

5

Fig 7.3 Example 7.1.

RB

RC

2 k

Q1

+12 V

VCE

2 4 6 8 10 12

2

4

6

8

IC

IC(sat)

VCE(off)

Plot the dc load line for the circuit shown in Fig. 7.3a.

6

Fig 7.4 Example 7.2.Plot the dc load line for the circuit shown in Fig. 7.4. Then, find the values of VCE for IC = 1, 2, 5 mA respectively.

RB

RC

1 k

Q1

+10 V

VCE

2 4 6 8 10

2

4

6

8

IC

10 IC (mA) VCE (V)

1 9

2 8

5 5

CE CC C CV V I R

7

Fig 7.6-8 Optimum Q-point with amplifier operation.

βC BI I

CE CC C CV V I R

VCE

IB = 0 A

IB = 10 A

IB = 20 A

IB = 30 A

IB = 40 A

IB = 50 A

IC

Q-Point

VCC

VCC

/2

IC(sat)

IC(sat)

/2

IB

8

Fig 7.9 Base bias (fixed bias).

CC BEB

B

V VI

R

βC BI I

CE CC C CV V I R

RC

RB

+0.7 V

IC

IB

IE

Input

Output

VBE

VCC

Q1

b = dc current gain = hFE

9


RC

2 kR

B

360 k

+0.7 V

IC

IB

IE

VBE

+8 V

hFE

= 100

0.7V 8V 0.7V

360kΩ20.28μA

CCB

B

VI

R

100 20.28μA2.028mA

C FE BI h I

8V 2.028mA 2kΩ3.94V

CE CC C CV V I R

The circuit is midpoint biased.

10


Construct the dc load line for the circuit shown in Fig. 7.10, and plot the Q-point from the values obtained in Example 7.3. Determine whether the circuit is midpoint biased.

VCE

(V)2 4 6 8 10

1

2

3

4

IC (mA)

Q

(sat )

8V4mA

2kΩCC

C

C

VI

R

off8VCCCE

V V

11

Fig 7.13 Base bias characteristics. (1)

RC

RB

+0.7 V

IC

IB

IE

Input

Output

VBE

VCC

Q1 Advantage: Circuit simplicity.

Disadvantage: Q-point shift with temp.

Applications: Switching circuits only.

Circuit recognition: A single resistor (RB) between the base terminal and VCC. No emitter resistor.

12

Fig 7.13 Base bias characteristics. (2)

RC

RB

+0.7 V

IC

IB

IE

Input

Output

VBE

VCC

Q1

(sat )

(off )

CCC

C

CE CC

VI

R

V V

Load line equations:

Q-point equations:

CC BEB

B

C FE B

CE CC C C

V VI

R

I h I

V V I R

13

Fig 7.14 Voltage divider bias. (1)

R1

R2 R

E

RC

+VCC

Input

Output

I1

I2 I

E

IB

IC

Assume that I2 > 10IB.

2

1 2

B CC

RV V

R R

0.7VE BV V

EE

E

VI

R

Assume that ICQ IE (or hFE >> 1). Then

CEQ CC CQ C EV V I R R

14

Fig 7.19-20 Base input resistance. (1)

R1

R2 R

E

RC

VCC

I1

I2

IE

IB

IC

RIN(base)

R1

R2

I1

I2

VCC

0.7 V

IB

RIN(base)

( 1)E E E B FE EV I R I h R

(base) ( 1)EIN FE E

B

FE E

VR h R

I

h R

May be ignored.

15

Fig 7.19-20 Base input resistance. (2)

IB

R1

R2

I1

I2

VCC

IB

RIN(base)

VB

2 (base)

1 2 (base)

2

1 2

21

//

//

//

//

//

IN

B CC

IN

FE E

CC

FE E

EQ

CC

EQ FE EEQ

R RV V

R R R

R h RV

R R h R

RV

R R h RR R

16

Fig 7.24 Voltage-divider bias characteristics. (1)

R1

R2 R

E

RC

+VCC

Input

Output

I1

I2 I

E

IB

IC

Circuit recognition: The voltage divider in the base circuit.

Advantages: The circuit Q-point values are stable against changes in hFE.

Disadvantages: Requires more components than most other biasing circuits.

Applications: Used primarily to bias linear amplifier.

17

Fig 7.24 Voltage-divider bias characteristics. (2)

R1

R2 R

E

RC

+VCC

Input

Output

I1

I2 I

E

IB

IC

Load line equations: (sat )

(off )

CCC

C E

CE CC

VI

R R

V V

Q-point equations (assume that hFERE > 10R2):

2

1 2

0.7V

B CC

E B

ECQ E

E

CEQ CC CQ C E

RV V

R R

V V

VI I

R

V V I R R

18

Other Transistor Biasing Circuits

• Emitter-bias circuits

• Feedback-bias circuits

–Collector-feedback bias

–Emitter-feedback bias

19

Fig 7.25-6 Emitter bias.

Assume that the transistor operation is in active region.

RC

RE

RB

IC

IE

IB

Q1

Input

Output

+VCC

-VEE

0.7V

1

EEB

B FE E

VI

R h R

C FE BI h I

1E FE BI h I

CE CC C C E E EEV V I R I R V

Assume that hFE >> 1.

CE CC C C E EEV V I R R V

20

Load Line forEmitter-Bias Circuit

(sat )

( )CC EE CC EEC

C E C E

V V V VI

R R R R

( )CE off CC EE CC EEV V V V V

VCE

IC

IC(sat)

VCE(off)

21

Fig 7.28 Emitter-bias characteristics. (1)

RC

RE

RB

IC

IE

IB

Q1

Input

Output

+VCC

-VEE

Circuit recognition: A split (dual-polairty) power supply and the base resistor is connected to ground.

Advantage: The circuit Q-point values are stable against changes in hFE.

Disadvantage: Requires the use of dual-polarity power supply.

Applications: Used primarily to bias linear amplifiers.

22

Fig 7.28 Emitter-bias characteristics. (2)

RC

RE

RB

IC

IE

IB

Q1

Input

Output

+VCC

-VEE

Load line equations:

(sat )

(off )

CC EEC

C E

CE CC EE

V VI

R R

V V V

Q-point equations:

1

BE EECQ FE

B FE E

CEQ CC CQ C E EE

V VI h

R h R

V V I R R V

23

Fig 7.29 Collector-feedback bias.

RB

RC

+VCC

IC

IE

IB

CC C B C B B BEV I I R I R V

( 1)

CC BEB

FE C B

V VI

h R R

CQ FE BI h I

1CEQ CC FE B C

CC CQ C

V V h I R

V I R

24

Circuit Stability ofCollector-Feedback Bias

RB

RC

+VCC

IC

IE

IB

hFE increases

IC increases (if IB is the same)

VCE decreases

IB decreases

IC does not increase that much.

Good Stability. Less dependent on hFE and temperature.

25

Collector-FeedbackCharacteristics (1)

RB

RC

+VCC

IC

IE

IB

Circuit recognition: The base resistor is connected between the base and the collector terminals of the transistor.

Advantage: A simple circuit with relatively stable Q-point.

Disadvantage: Relatively poor ac characteristics.


26

Collector-FeedbackCharacteristics (2)

RB

RC

+VCC

IC

IE

IB

Q-point relationships:

( 1)

CC BEB

FE C B

V VI

h R R

CQ FE BI h I

CEQ CC CQ CV V I R

27

Fig 7.31 Emitter-feedback bias.

RB

RC

+VCC

RE

IB

IE

IC

1

CC BEB

B FE E

V VI

R h R

CQ FE BI h I

CEQ CC C C E E

CC CQ C E

V V I R I R

V I R R

1E FE BI h I

28

Circuit Stability ofEmitter-Feedback Bias

hFE increases

IC increases (if IB is the same)

VE increases

IB decreases

IC does not increase that much.

IC is less dependent on hFE and temperature.

RB

RC

+VCC

RE

IB

IE

IC

29

Emitter-FeedbackCharacteristics (1)

Circuit recognition: Similar to voltage divider bias with R2

missing (or base bias with RE

added).

Advantage: A simple circuit with relatively stable Q-point.

Disadvantage: Requires more components than collector-feedback bias.


RB

RC

+VCC

RE

IB

IE

IC

30

Emitter-FeedbackCharacteristics (2)

RB

RC

+VCC

RE

IB

IE

IC

Q-point relationships:

( 1)

CC BEB

B FE E

V VI

R h R

CQ FE BI h I

CEQ CC CQ C EV V I R R

31

Summary

• DC Biasing and the dc load line

• Base bias circuits

• Voltage-divider bias circuits

• Emitter-bias circuits

• Feedback-bias circuits

–Collector-feedback bias circuits

–Emitter-feedback bias circuits

Transistors

Lecture Overview

• What is a Transistor?

• History

• Types

• Characteristics

• Applications

What is a Transistor?

• Semiconductors: ability to change from conductor to insulator

• Can either allow current or prohibit current to flow

• Useful as a switch, but also as an amplifier

• Essential part of many technological advances

A Brief History

• Guglielmo Marconi invents radio in 1895

• Problem: For long distance travel, signal must be amplified

• Lee De Forest improves on Fleming’s original vacuum tube to amplify signals

• Made use of third electrode

• Too bulky for most applications

The Transistor is Born

• Bell Labs (1947): Bardeen, Brattain, and Shockley

• Originally made of germanium

• Current transistors made of doped silicon

How Transistors Work• Doping: adding small amounts of other

elements to create additional protons or electrons

• P-Type: dopants lack a fourth valence electron (Boron, Aluminum)

• N-Type: dopants have an additional (5th) valence electron (Phosphorus, Arsenic)

• Importance: Current only flows from P to N

Diodes and Bias

• Diode: simple P-N junction.

• Forward Bias: allows current to flow from P to N.

• Reverse Bias: no current allowed to flow from N to P.

• Breakdown Voltage: sufficient N to P voltage of a Zener Diode will allow for current to flow in this direction.

• 3 adjacent regions of doped Si (each connected to a lead):

– Base. (thin layer,less doped).

– Collector.

– Emitter.

• 2 types of BJT:

– npn.

– pnp.

• Most common: npn (focus on it).

Bipolar Junction Transistor (BJT)

npn bipolar junction transistor

pnp bipolar junction transistorDeveloped by Shockley (1949)

• 1 thin layer of p-type, sandwiched between 2 layers of n-type.• N-type of emitter: more heavily doped than collector.• With VC>VB>VE:

– Base-Emitter junction forward biased, Base-Collector reverse biased.– Electrons diffuse from Emitter to Base (from n to p).– There’s a depletion layer on the Base-Collector junction no flow of e-

allowed.– BUT the Base is thin and Emitter region is n+ (heavily doped)

electrons have enough momentum to cross the Base into the Collector.– The small base current IB controls a large current IC

BJT npn Transistor

• Current Gain:– α is the fraction of electrons

that diffuse across the narrow Base region

– 1- α is the fraction of electrons that recombine with holes in the Base region to create base current

• The current Gain is expressed in terms of the β (beta) of the transistor (often called hfe by manufacturers).

• β (beta) is Temperature and Voltage dependent.

• It can vary a lot among transistors (common values for signal BJT: 20 - 200).

BJT characteristics

1

)1(

B

C

EB

EC

I

I

II

II

• Emitter is grounded.

• Base-Emitter starts to conduct with VBE=0.6V,IC flows and it’s IC=*IB.

• Increasing IB, VBE slowly increases to 0.7V but IC rises exponentially.

• As IC rises ,voltage drop across RC increases and VCE drops toward ground. (transistor in saturation, no more linear relation between ICand IB)

npn Common Emitter circuit

Common Emitter characteristics

No current flows

Collector current controlled by the collector circuit. (Switch behavior)

In full saturation VCE=0.2V.

Collector current proportional to Base current

The avalanche multiplication of current through collector junction occurs: to be avoided

Operation

Region

IB or VCE

Char.

BC and BE

Junctions

Mode

Cutoff IB = Very small

Reverse & Reverse

Open Switch

Saturation VCE = Small Forward & Forward

Closed Switch

Active

Linear

VCE = Moderate

Reverse &

Forward

Linear Amplifier

Break-

down

VCE = Large

Beyond Limits

Overload

Operation region summary

BJT as Switch

•Vin(Low ) < 0.7 V•BE junction not forward biased•Cutoff region•No current flows•Vout = VCE = Vcc

•Vout = High

•Vin(High)•BE junction forward biased (VBE=0.7V)

•Saturation region•VCE small (~0.2 V for saturated BJT)•Vout = small•IB = (Vin-VB)/RB

•Vout = Low

• Basis of digital logic circuits

• Input to transistor gate can be analog or digital

• Building blocks for TTL – Transistor Transistor Logic

• Guidelines for designing a transistor switch:– VC>VB>VE

– VBE= 0.7 V

– IC independent from IB (in saturation).

– Min. IB estimated from by (IBminIC/).

– Input resistance such that IB > 5-10 times IBmin because varies among components, with temperature and voltage and RB

may change when current flows.

– Calculate the max IC and IB not to overcome device specifications.

BJT as Switch 2

•Common emitter mode•Linear Active Region•Significant current Gain

Example:•Let Gain, = 100

•Assume to be in active region -> VBE=0.7V

•Find if it’s in active region

BJT as Amplifier

BJT as Amplifier

V

VRIRIVV

mAII

mARR

VVI

IIII

VV

BEEECCCCCB

BC

EB

BEBBB

BCBE

BE

93.3

7.0)0107.0*101)(2()07.1)(3(10

**

07.10107.0*100*

0107.0402

7.05

101*

)1(

7.0

VCB>0 so the BJT is in active region

Field Effect Transistors

• Similar to the BJT:

– Three terminals,

– Control the output current

• In 1925, the fundamental principle of FET transistors was establish by Lilienfield.

• 1955 : the first Field effect transistor works

• Increasingly important in mechatronics.

BJT Terminal

FET Terminal

Base Gate

Collector Drain

Emitter Source

Field Effect Transistors

• Three Types of Field Effect Transistors

– MOSFET (metal-oxide-semiconductor field-effect transistors)

– JFET (Junction Field-effect transistors)

– MESFET (metal-semiconductor field-effect transistors)

• The more used one is the n-channel enhancement mode MOSFET, also called NMOS

• Two Modes of FETs

– Enhancement mode

– Depletion mode

Enhanced MOSFET

Depleted MOSFET

FET Architecture

JFET

Conducting

Region

Nonconducting

Region

Nonconducting

Region

NMOS Voltage Characteristic

Active Region

Saturation Region

VGS < Vth

IDS=0

VGS > Vth :

0 < VDS < VPinch off

Active RegionIDS controlled by VGS

VDS > VBreakdown

IDS approaches IDSShort

Should be avoided

VDS > VPinch off

Saturation RegionIDS constant

VDS = Constant

2

1

TH

GS

DSSHORTDSV

VII

VPinchoff

NMOS uses

• High-current voltage-controlled switches

• Analog switches

• Drive DC and stepper motor

• Current sources

• Chips and Microprocessors

• CMOS: Complementary fabrication

JFET overview

The circuit symbols:

JFET design:

Junction Field Effect Transistor

– VGS > Vth

IDS=0

VGS < -Vth :

0 < VDS < VPinch off

Active Region

IDS controlled by VGS

VDS > VPinch off

Saturation Region

IDS constant

VDS > VBreakdown

IDS approaches

IDSShort

Should be avoided

Difference

from NMOS

VPinchoff

Active Region

Saturation Region

2

1

TH

GS

DSSHORTDSV

VII

JFET uses

• Small Signal Amplifier

• Voltage Controlled Resistor

• Switch

FET Summary• General:

• Signal Amplifiers• Switches

JFET:For Small signals

Low noise signalsBehind a high impedence systemInside a good Op-Ampl.

MOSFET:QuickVoltage Controlled ResistorsRDS can be really low : 10 mOhms

• In General– Fabrication is different in order to:

• Dissipate more heat

• Avoid breakdown

– So Lower gain than signal transistors

• BJT– essentially the same as a signal level BJT

– Power BJT cannot be driven directly by HC11

• MOSFET– base (flyback) diode

– Large current requirements

Power Transistors

Other Types of Transistors

Various Types of Transistors

• TempFET – MOSFET’s with temperature sensor

• High Electron Mobility Transistors (HEMTs) –allows high gain at very high frequencies

• Darlington – two transistors within the same device, gain is the product of the two inidvidual transistors

Shockley Diode/Thyristor

• Four-layer PNPN semiconductor devices

• Behaves as two transistors in series

• Once on, tends to stay on

• Once off, tends to stay off

TRIAC

• Triode alternating current switch

• Essentially a bidirectional thyristor

• Used in AC applications

• Con: Requires high current to turn on

• Example uses: Modern dimmer switch

References

• www.lucent.com

• http://transistors.globalspec.com

• http://www.kpsec.freeuk.com

• www.Howstuffworks.com

• www.allaboutcircuits.com

• Previous student lectures

http://www.lucent.com/

http://transistors.globalspec.com/

http://www.kpsec.freeuk.com/

http://www.howstuffworks.com/

http://www.allaboutcircuits.com/

Zener Diode

Outlines

Introduction of Zener Diode

Construction of Zener Diode

Working of Zener Diode

Application of Zener Diode

Numerical of Zener Diode

Introduction

The zener diode is a silicon pn junction devices that differs from rectifier

diodes because it is designed for operation in the reverse-breakdown

region. The breakdown voltage of a zener diode is set by carefully

controlling the level during manufacture. The basic function of zener

diode is to maintain a specific voltage across it’s terminals within given

limits of line or load change. Typically it is used for providing a stable

reference voltage for use in power supplies and other equipment.

Construction of ZenerZener diodes are designed to operate in reverse breakdown. Two types of reverse

breakdown in a zener diode are avalanche and zener. The avalanche break down

occurs in both rectifier and zener diodes at a sufficiently high reverse voltage. Zener

breakdown occurs in a zener diode at low reverse voltages.

A zener diode is heavily doped to reduced the breakdown voltage.

This causes a very thin depletion region.

The zener diodes breakdown characteristics are determined by the

doping process

Zeners are commercially available with voltage breakdowns of 1.8 V

to 200 V.

Working of Zener

A zener diode is much like a normal diode. The exception being is that it

is placed in the circuit in reverse bias and operates in reverse breakdown.

This typical characteristic curve illustrates the operating range for a zener.

Note that it’s forward characteristics are just like a normal diode.

Breakdown Characteristics

Figure shows the reverse portion of a zener diode’s characteristic

curve. As the reverse voltage (VR) is increased, the reverse current (IR)

remains extremely small up to the “knee” of the curve. The reverse

current is also called the zener current, IZ. At this point, the breakdown

effect begins; the internal zener resistance, also called zener impedance

(ZZ), begins to decrease as reverse current increases rapidly.

ZENER BREAKDOWN

• Zener and avalanche effects are responsible for such a dramatic increase in the value of current at the breakdown voltage.

• If the impurity concentration is very high, then the width of depletion region is very less. Less width of depletion region will cause high intensity of electric field to develop in the depletion region at low voltages.

• Lets take an example to understand things clearly.

• Let say the width of depletion region is 200 Å (very small). If a reverse bias voltage of just 4 V is applied to the diode, then the electric field intensity in the depletion region will be

4 = 2 x 108 V/m200 x 10-10

.

• Merely a voltage of 4 V is responsible to generate

an electric field intensity of 2 x 108 V/m (very high

intensity).

• This electric field is sufficient to rupture the bonds

and separate the valence electrons from their

respective nuclei.

• Large number of electrons gets separated from

their atoms, resulting in sudden increase in the

value of reverse current.

• This explanation was given by scientist C. E.

Zener. Such diodes are called Zener diodes.

• Zener effect predominates in diodes whose

breakdown voltage is below 6 V.

AVALANCHE BEAKDOWN

• Zener effect predominates on diodes whose

breakdown voltage is below 6 V. The breakdown

voltage can be obtained at a large value by reducing

the concentration of impurity atom.

• We know that very little amount of current flows in

the reverse biased diode. This current is due to the

flow of minority charge carriers i.e., electrons in the

p type semiconductor and holes in the n type

semiconductor.

.

• The width of depletion region is large when the

impurity concentration is less.

• When a reverse bias voltage is applied across the

terminals of the diode, the electrons from the p type

material and holes from the n-type materials

accelerates through the depletion region.

• This results in collision of intrinsic particles

(electrons and holes) with the bound electrons in the

depletion region. With the increase in reverse bias

voltage the acceleration of electrons and holes also

increases.

• Now the intrinsic particles collides with bound

electrons with enough energy to break its covalent

bond and create an electron-hole pair. This is shown

in the figure.

Avalanche Breakdown

Mechanism

.

• The collision of electrons with the atom creates an

electron-hole pair. • This newly created electron also gets accelerated

due to electric field and breaks many more

covalent bond to further create more electron-hole

pair. • This process keeps on repeating and it is

called carrier multiplication. • The newly created electrons and holes contribute

to the rise in reverse current. • The process of carrier multiplication occurs very

quickly and in very large numbers that there is

apparently an avalanche of charge carriers.

Thus the breakdown is called avalanche

breakdown.

DIFFERENCE BETWEEN ZENER

AND AVALANCHE BREAKDOWNZener Breakdown

1.This occurs at junctions which being

heavily doped have narrow depletion

layers

2. This breakdown voltage sets a

very strong electric field across

this narrow layer.

3. Here electric field is very strong

to rupture the covalent bonds

thereby generating electron-hole

pairs. So even a small increase in

reverse voltage is capable of producing

Large number of current carriers.

4. Zener diode exhibits negative temp:

coefficient. Ie. breakdown voltage

decreases as temperature increases.

Avalanche breakdown1. This occurs at junctions which

being lightly doped have wide depletion layers.

2. Here electric field is not strong

enough to produce Zener breakdown.

3. Her minority carriers collide with semi

conductor atoms in the depletion region, which

breaks the covalent bonds and electron-hole

pairs are generated. Newly generated charge

carriers are accelerated by the electric field

which results in more collision and generates

avalanche of charge carriers. This results in

avalanche breakdown.

4. Avalanche diodes exhibits positive temp:

coefficient. i.e breakdown voltage increases

with increase in temperature.

Zener diode Data Sheet Information

VZ: zener voltage

IZT

: zener test current

ZZT

: zener Impedance

IZK

: zener knee

current IZM

: maximum

zener current

Ideal Model & Ideal Characteristic Curve of Zener Diode

Practical Model & Ideal Characteristic Curve of Zener Diode

Zener Diode Applications –

Zener Regulation with a Varying Input Voltage

Zener Limiting

Zener diodes can used in ac applications to limit voltage swings to

desired levels.

VZ: zener voltage

Vd: Diode voltage

Vd = 0.7

Numerical of Zener Diode

A zener diode exhibits a certain change in V z for a certain

change in lz on a portion of the linear characteristic curve

between IZK and IZM as illustrated in Figure. What is the zener

impedance?

Temperature Coefficient • The temperature coefficient specifies the percent change

in zener voltage for each degree centigrade change in temperature.

• For example, a 12 V zener diode with a positive temperature coefficient of 0.01% /OC will exhibit a 1.2 mV increase in Vz when the junction temperature increases one degree centigrade.

• The formula for calculating the change in zener voltage for a given junction temperature change, for a specified temperature coefficient, is

Where Vz is nominal zener voltage at 250C. When temp.

coefficient is expressed in mV/0C

Example• A 5.0V stabilised power supply is

required to be produced from

a 12V DC power supply input

source.

The maximum power rating Pz of

the zener diode is 2W.

Using the zener regulator circuit

calculate:

a) The maximum current flowing

through the zener diode.

b) The value of the series

resistor, Rs

c) The load current IL if a load

resistor of 1kΩ is connected

across the Zener diode.

d) The total supply current Is

(a)

(b)

(c)

(d)

Zener Diode Voltages

• As well as producing a single stabilised voltage output, zener diodes can also be connected together in series along with normal silicon signal diodes to produce a variety of different reference voltage output values

• The values of the individual Zener diodes can be chosen to suit the application while the silicon diode will always drop about 0.6 - 0.7V in the forward bias condition.

• The supply voltage, Vin must of course be higher

than the largest output reference voltage

Summary

• A zener diode is always operated in its reverse biased condition.

• A voltage regulator circuit can be designed using a zener diode to maintain a constant DC output voltage across the load in spite of variations in the input voltage or changes in the load current.

• The zener voltage regulator consists of a current limiting resistor Rs connected in series with the input voltage Vs with the zener diode connected in parallel with the load RL in this reverse biased condition.

• The stabilized output voltage is always selected to be the same as the breakdown voltage Vz of the diode.

The Battery

Types of Batteries

The primary battery converts chemical energy

to electrical energy directly, using the chemical

materials within the cell to start the action.

The secondary battery must first be charged

with electrical energy before it can convert

chemical energy to electrical energy.

The secondary battery is frequently called a

storage battery, since it stores the energy that is

supplied to it.

DRY CELL

• Uses An electrolytic paste.

• The electrolytic paste

reacts with the electrodes

to produce a negative

charge on one electrode

and a positive charge on

the other.

• The difference of potential

between the two

electrodes is the output

voltage.

Lead Acid Battery

• Electrolyte for the

most part distilled

(pure) water, with

some sulfuric acid

mixed with the water.

• Electrodes must be of

dissimilar metals.

• An active electrolyte.

Cells

• Positive electrode

• Negative electrode

• Electrolyte

• Separator

The basic primary wet cell• The metals in a cell are called

the electrodes, and the chemical

solution is called the

electrolyte.

• The electrolyte reacts

oppositely with the two

different electrodes

• It causes one electrode to lose

electrons and develop a positive

charge; and it causes one other

electrode to build a surplus of

electrons and develop a

negative charge.

• The difference in potential

between the two electrode

charges is the cell voltage.

The Electrolyte

• When charging first started,

electrolysis broke down each

water molecule (H2O) into two

hydrogen ions (H+) and one

oxygen ion (O-2).

• The positive hydrogen ions

attracted negative sulfate ions

(SO4-2) from each electrode.

• These combinations produce

H2SO4, which is sulfuric acid.

Electrolysis

• The producing of

chemical changes by

passage of an electric

current through an

electrolyte.

Specific Gravity

• Ratio of the weight of

a given volume of a

substance to the

weight of an equal

volume of some

reference substance,

or, equivalently, the

ratio of the masses of

equal volumes of the

two substances.

• Example: It is the

weight of the sulfuric

acid - water mixture

compared to an equal

volume of water. Pure

water has a specific

gravity of 1,000.

Hydrometer

• Device used to determine directly the specific

gravity of a liquid.

Hydrometer

The chart below gives state of charge vs.

specific gravity of the electrolyte.

State of Charge Specific

Gravity

• 100% Charged 1.265

• 75% Charged 1.239

• 50% Charged 1.200

• 25% Charged 1.170

• Fully Discharged 1.110

• These readings are correct at 75°F

•If you are simply using an accurate voltmeter, along with occasional checks with your hydrometer, this

chart should be helpful in determining your batteries state of charge.

Charge Level Specific Gravity Voltage 2V n Voltage 6V n Voltage 12V n Voltage 24V n

100.00% 1.270 2.13 6.38 12.75 25.50

75.00% 1.224 2.08 6.24 12.48 24.96

50.00% 1.170 2.02 6.06 12.12 24.24

20.00% 1.097 1.94 5.82 11.64 23.28

0.00% 1.045 1.89 5.67 11.34 22.68

n stands for nominal voltage

Voltmeter = Hydrometer

Ohm’s Law

• Ohm’s Law can be expressed by the

equation:

– E = IR

– I = E/R

– R = E/I

Ohm’s Law

• Series circuits, the total voltage is equal to

the sum of the individual voltages. The

current is constant.

• Parallel circuits, the voltage is constant.

The current is equal to the sum of the

individual currents.

Series Connected Batteries

• Positive terminal of one

cell is connected to the

negative terminal of the

next, is called a series

connected battery.

• The voltage of this type of

battery is the sum of a

individual cell voltages.

Parallel Connected Batteries

• Connect the negative

terminal from one cell to

the negative of the next

cell

• Connect the positive

terminal to the positive

terminal, is parallel

connected.

• Voltage remains constant

and the current is

cumulative.

Series-Parallel Connections

PARALLEL

SERIES

SERIES-

PARALLEL

SERIES

SERIES

Preventive Maintenance

• When the top of a battery is “dirty or looks damp.

• Give a battery a general cleaning, use hot

water (130° F to 170° F) with a neutralizer /

detergent solution.

Charging

• Chemical reaction occur during charging.

• Lead sulfate on both plates is separated into Lead

(Pb).

• Sulfate (SO4) leaves both plates.

• It combines with hydrogen (H) in the electrolyte to

form sulfuric acid (H2SO4).

• Oxygen (O) combines with the lead (Pb) at the

positive plate to form lead oxide (PbO2).

• The negative returns to original form of lead (Pb.

Charging

• Clean Battery Terminals.

• Attach clamps to the battery in proper polarity.

• Keep open flames and sparks away from battery.

• Ventilate the battery well while charging.

Charging

• The charge a battery receives is equal to the

charge rate in amperes multiplied by the

time in hours.

• Measure the specific gravity of a cell once

per hour during charging to determine full

charge.

Ventilation Requirements

• The oxygen and hydrogen gases released during

the gassing phase of a typical flooded lead-acid

battery recharge can be dangerous if allowed to

exceed 0.8 % (by volume) or 20 percent of the

lower explosive range. Concentrations of

hydrogen between 4 % and 74% are considered

explosive (40,000 ppm and 740,000 ppm).

HYDROGEN• Chemical Formula: H2

• Specific Gravity: 0.0695

• Color: None Odor: None

• Taste: None

• Origin: Applying water to super hot mine fires, explosions electrolysis of

battery acid.

• Explosive Range: 4.1% - 74%

• Ignition Temp: 1030o - 1130o F

• % Oxygen Needed To Burn or Explode: 5%

• TLV: None

• STEL: None

• Effect on Body:Asphxysiant Due to Displacement of Oxygen.

• How Detected: Electronic Detectors, Squeeze Tube Detectors, Chemical

Analysis.

• NOTE: Hydrogen is the reason a flame safety lamp is not permitted in a battery

charging station.

Ventilation

• All lead acid power batteries give off gases

when recharging and also for a period after

the charge is completed.

– A Concentration of hydrogen in excess of 4%

(by volume). It is suggested that the

concentration be controlled to a maximum of

2% (by volume).

Solar cells

Overview

Solar cell fundamentals

Novel solar cell structures

Thin film solar cells

Next generation solar cell

Appealing Characteristics

Consumes no fuel

No pollution

Wide power-handling capabilities

High power-to-weight ratio

Solar Energy Spectrum

Power reaching earth 1.37 KW/m2

Air Mass

Amount of air mass through which light pass

Atmosphere can cut solar energy reaching earth by 50% and more

Solar cell – Working Principle

Operating diode in fourth quadrant generates power

Overview





Back Surface Fields

Most carriers are generated in thicker p region

Electrons are repelled by p-p+ junction field

Schottky Barrier Cell

Principle similar to p-n junction cell

Cheap and easy alternative to traditional cell

Limitations:

Conducting grid on top of metal layer

Surface damage due to high temperature in grid-attachment technique

Grooved Junction Cell

Higher p-n junction area

High efficiency ( > 20%)

Overview





Thin Film Solar Cells

Produced from cheaper polycrystalline materials and glass

High optical absorption coefficients

Bandgap suited to solar spectrum

Inverted Thin Film Cell

p-diamond (Bandgap 5.5 eV) as a window layer

n-CdTe layer as an absorption layer

Efficiency Losses in Solar Cell

1 = Thermalization loss

2 and 3 = Junction and contact voltage loss

4 = Recombination loss

Overview





Dec 7, 2009

Electromagnetic

Induction

Dec 7, 2009 Physics 1 (Garcia) SJSU

Electromagnetic Induction

Voltage is induced whether the magnetic field of a

magnet moves near a stationary conductor or

the conductor moves in a stationary magnetic

field.


Demo: Magnet Induces Current

Voltage is induced when a magnet moves towards

or away from a coil, inducing a current in the coil.

Faster the magnet’s motion, the greater the

induced current.

Note: Do this in lab too.


Magnetic Recording

Write data by magnetizing

recording media (e.g.,

video tape, hard disk)

using electromagnets.

Data is read back using the

induced current produced

when magnetized media

moves past receiver coils

(reverse of writing data).Hard disk


Electric Generator

Electric generator moves a conductor in a

magnetic field to produce voltage via

electromagnetic induction


Demo: Electric Generator

Turn the shaft by hand and as the coils pass the magnets a voltage is induced.

DC current is generated.

Magnet

Magnet

Coils

DC Output

S

H

A

F

T



Induction: No Free Lunch

Takes work to turn

the generator crank

to produce electric

current.

The faster we turn

the crank to

produce more

current, the more

difficult it is to turn.

More difficult to push the magnet into a coil with more loops because the magnetic field of each current loop resists the motion of the magnet.


Faraday’s Law

The induced voltage in a coil is proportional to the

product of the number of loops and rate at which

the magnetic field changes within the loops.

Small

VoltageMedium

Voltage

LargeVoltage

Demo: Electromagnetic Oscillations

Connect to

alternating

current (AC)

Oscillating

Magnetic

Field

Electro-

Magnet

Put alternating current into an

electromagnet and you create

an oscillating magnetic field.

This oscillating magnetic field

induces electrical currents by

inducing electrical field

oscillations.

This is, effectively, a very low

frequency electromagnetic

antenna.

Coil with bulb

Demo: Electric Motor

Can create an electrical motor by passing a

current through a set of electro-magnets

mounted on a rotating shaft.

Current inCurrent out

Electro-magnets

Electric Motor, Analyzed

Electromagnet mounted on a shaft with opposing magnets on each side.

Current direction always such that electromagnet is repelled, causing shaft to turn.

N SN S

N S

N S

Current

Current


Demo: Generator Becomes Motor

Pass a current into the generator and it

becomes an electric motor.

Rotor

Spins

Magnet

Magnet

DC Input

Battery



Self-Induction

When a current is

induced by a

changing magnetic

field, that current

itself produces its

own magnetic field.

This effect is called

self-induction.

Current

Primary Magnetic Field

Self-Induced

Magnetic Field


Demo: Lenz’s Law

Connect to

alternating

current (AC)

Oscillating

Magnetic

Field

Electro-

Magnet

Metal ring is

levitated by

self-induced

secondary

magnetic field

Induced current

produces a

secondary magnetic

field that is always

opposed to the

primary magnetic

field that induced it,

an effect called

Lenz’s law.


Check Yourself

Does the ring levitate if we connect

the electromagnet to direct

current (e.g., to a battery)?

Does the ring levitate if it has a

gap?Electro-

Magnet


Check Yourself

Connect to

alternating

current (AC)

Oscillating

Magnetic

Field

Electro-

Magnet

Hold the ring down on the shaft and it

starts to get hot. Why?

What if we cool the ring in liquid

nitrogen and repeat the demo?


Demo: Magnetic Brakes

Strong magnet dropped into

a copper pipe falls slowly

due to secondary magnetic

field induced by its motion.

Great America’s Drop Zone

has a 22 story freefall,

lasting four seconds,

decelerated by magnetic

braking.


Eddy Currents

Changing magnetic field

induces eddy currents

within any conductor.

These internal currents

produce self-induced

magnetic fields, which

by Lenz’s law are in

opposition of the

primary magnetic field.

Eddy

Currents

Primary Magnetic Field

Self-Induced

Magnetic Field


Metal Detectors

Can detect the presence of metals by using a transmitter coil to create an oscillating primary magnetic field.

This creates a secondary magnetic field due to eddy currents in the metal.

Can detect this secondary magnetic field by using a receiver coil.


Demo: Back Electromotive Force

Changing magnetic field in an

electromagnet induces a voltage in the

electromagnet itself.

When we disconnect a large

electromagnet the magnetic field

rapidly collapses.

This changing magnetic field

self-induces a large voltage in

the coil of the electromagnet.

Large spark occurs at the switch.

Superhetrodyne Receiver

Receiver

Intercept the electromagnetic waves inthe receiving antenna to produce thedesired RF modulated carrier.•Select the desired signal and reject theunwanted signal.•Amplify the RF signal.•Detect the RF carrier to get back theoriginal modulation frequency voltage.•Amplify the modulation frequencyvoltage

Features of ReceiverSimplicity of operation• Good fidelity• Good selectivity• Average sensitivity•Adaptability to different types of aerials

If Receiver has Poor Selectivity

If Receiver has Poor Sensitivity

If Receiver has Poor fidelity

Superhetrodyne Receiver

Gang TuningThe adjustment for the center frequencyof the pre selector and the adjustmentfor local oscillator are gang tuned.The two adjustments are mechanicallytied together and single adjustment willchange the center frequency of the preselector and the local oscillator

TRACKING:It is the ability of the local oscillator in a receiver to oscillate either above or below the selected radio frequency carrier by an amount equal to the IF frequency through the entire radio frequency band.

•WAVE PROPAGATION.•TYPES OF PROPAGTION.•GROUND WAVE PROPAGATION.•SKY WAVE PROPAGATION.•SPACE WAVE PROPAGATION

WAVE PROPAGATIONWave propagation is any of the ways in whichwaves travel. With respect to the direction ofthe oscillation relative to the propagationdirection, we can distinguish betweenlongitudinal wave and transverse waves. Forelectromagnetic waves, propagation mayoccur in a vacuum as well as in a materialmedium. Other wave types cannot propagatethrough a vacuum and need a transmissionmedium to exist.

TYPES OF PROPAGATION•GROUND WAVE PROPAGATION•SKY WAVE PROPAGATION•SPACE WAVE PROPAGATION

ANTENNAS

INTRODUCTION• An antenna is an electrical device which convertselectric currents into radio waves, and vice versa. Itis usually used with a radio transmitter or radioreceiver.• In transmission, a radio transmitter applies anoscillating radio frequency electric current to theantenna's terminals, and the antenna radiates theenergy from the current as electromagnetic waves(radio waves).

RADIATION PATTERN

The radiation pattern of an antenna is a plot of therelative field strength of the radio waves emitted bythe antenna at different angles.• It is typically represented by a three dimensionalgraph, or polar plots of the horizontal and verticalcross sections. It is a plot of field strength in V/mversus the angle in degrees.• The pattern of an ideal isotropic antenna , whichradiates equally in all directions, would look like asphere.• Many non-directional antennas, such as dipoles,emit equal power in all horizontal directions, withthe power dropping off at higher and lower angles;this is called an Omni directional pattern.

BEAM-WIDTH• Beam-width of an antenna is definedas angular separation between the twohalf power points on power densityradiation pattern OR• Angular separation between two 3dBdown points on the field strength ofradiation pattern• It is expressed in degrees

ISOTROPIC ANTENNA• Isotropic antenna or isotropic radiator is ahypothetical (not physically realizable)concept, used as a useful reference todescribe real antennas.• Isotropic antenna radiates equally in alldirections. – Its radiation pattern isrepresented by a sphere whose centercoincides with the location of the isotropicradiator.

•It is considered to be a point in spacewith no dimensions and no mass.This antenna cannot physically exist,but is useful as a theoretical modelfor comparison with all otherantennas.• Most antennas' gains are measuredwith reference to an isotropicradiator, and are rated in dBi(decibels with respect to an isotropicradiator).

HALF WAVE DIPOLE ANTENNA• The half-wave dipole antenna is just a specialcase of the dipole antenna.• Half-wave term means that the length of thisdipole antenna is equal to a half-wavelength at thefrequency of operation.• The dipole antenna, is the basis for most antennadesigns, is a balanced component, with equal butopposite voltages and currents applied at its twoterminals through a balanced transmission line

DIGITAL MODULATION TECHNIQUES

INTRODUCTION

• In a digital communication system,the source to be transmitted is discreteboth in time and amplitude• The source information is normallyrepresented as a baseband (low-pass)signal• In digital modulation a highfrequency analog carrier signal ismodulated by digital bit stream

What is modulation ?• Modulation = Adding information to a carrier signal• The sine wave on which the characteristics of the information signalare modulated is called a carrier signal

Modulations Systems

Types of digital modulationtechniqueCoherent• Non coherentCoherent; In coherent modulationtechnique process received signal witha local carrier of same frequency andphase.Non coherent; In Non coherent digitalmodulation technique there is norequirement of reference wave.

Digital modulation Technique

• ASK (Amplitude shift keying)• PSK Phase shift keying• FSK Frequency shift keying

Amplitude shift keying

In ASK, the amplitude of the signal is changed in response toinformation. Bit 1 is transmitted by a signal of one particular amplitudeto transmit 0, we change the amplitude keeping the frequency constant.it is shown below

Phase shift keyingIn PSK,we change the phase of the sinusoidal carrier to indicateinformation . To transmit 0,we shift the phase of the sinusoidal by180 phase shift represents the change in the state of the information.

Frequency shift keyingIn FSK,we change the frequency in response to informationone particular frequency for 1 and another frequency for a 0.

Advantages• Digital modulation can easily detect andcorrect the noise.• Security is more in digital modulation.• Digital modulation signal can travels along distance.

AMPLIFIERAn electronic amplifier is a device for increasing the power of a signal. Itdoes this by taking energy from a power supply and controlling the output tomatch the input signal shape but with a larger amplitude. In this sense, anamplifier may be considered as modulating the output of the power supply

TYPES OF AMPLIFIERInverting AmplifierNon-Inverting Amplifier

OP-AMP (Operational Amplifier)An Operational Amplifier, or Op Amp, is a dual-input, single-output amplifier that exhibits a high open-loop gain, high input resistances, and a low output resistance. One of the inputs of an operational amplifier amp is non-inverting while the other is inverting.The output Vout of an operational amplifier without feedback (also known asopen-loop) is given by the formula: Vout = A(Vp-Vn) where A is the open-loopgain of the op amp, Vp is the voltage at the non-inverting input, and Vn is thevoltage at the inverting input.

INVERTING AMPLIFIERAmplifier whose output polarity is reversed as compared to its input;such an amplifier obtains its negative feedback by a connection fromoutput to input, and with high gain is widely used as an operationalamplifier.

GAIN (Av) = -Rf/R1

NON-INVERTING AMPLIFIERAn operational amplifier in which the input signal is applied to the ungrounded positive input terminal to give a gain greater than unity and make the output voltage change in phase with the input voltage.

GAIN (Av) = 1+RF/R2

D/A CONVERTERWeighted-register D/A converterR-2R ladder D/A converterWeighted-register D/A converterThe OP-Amp adder circuit is used to build a Weighted-register D/A converter by selecting input register that are weighted in binary progression.

Output Voltage (V0) = -RFV1/R1-RFV2/R2-RFV3/R3V0 = -(RFV1/R1+RFV2/R2+RFV3/R3)R=2R ladder D/A ConverterAn R-2R Ladder is a simple and inexpensive way to perform digitalt o-analogconversion, using repetitive arrangements of precision resistor networks in aladder-like configuration.As its name implies, the R-2R network consists of resistors with only two values,R and 2R (10K and 20K, respectively, in the circuit shown). The input SN to bit Nis '1' if it is connected to a voltage VR and '0' if it is grounded.

Analog to Digital ConverterAn analog-to-digital converter (abbreviated ADC, A/D or A to D) is adevice that converts a continuous quantity to a discrete digital number. Or Adevice that converts continuously varying analog signals from instrumentsand sensors that monitor conditions, such as sound, movement andtemperature into binary code for the computer. The A/D converter may becontained on a single chip or can be one circuit within a chip.

TYPES

Counting A/D ConverterDual slope A/D converterParallel A/D ConverterA/D Converter using voltage for frequency conversionA/D Converter using voltage to time conversion

OVERVIEWIntroduction.Characteristics.Resistor Transistor Logic.Diode Transistor Logic.Transistor-Transistor Logic.Emitter coupled Logic

Characteristics

Fan in : The number of inputs that the gate can handle properly with out disturbing the output level.

Fan out : The number of inputs that can driven simultaneously by the output with out disturbing the output level.

Noise immunity : Noise immunity is the ability of the logic circuit to tolerate the noise voltage.

Noise Margin : The quantities measure of noise immunity is called noise margin.Propagation Delay : The propagation delay of gate is the average transition delay time for the signal to propagate from input to output It is measured in nanosecondsThreshold Voltage : The voltage at which the circuit changes from one state to another stateOperating Speed : The speed of operation of the logic gate is the time that elapses between giving input and getting output.Power Dissipation : The power dissipation is defined as power needed by the logic circuit

Resistor Transistor LogicRTL is the first logic family which is not available in monolithic form.The basic circuit of the RTL logic family is the NOR.Each input is associated with one resistor and one transistor.The collector of the transistor are tied together at the outputThe voltage levels for the circuit are 0.2v for the low level and from 1 to 3.6v for the high level

CIRCUIT DIAGRAM

True Table

A B Y=A+B0 0 10 1 01 0 01 1 0

WorkingIf any input is high. The corresponding transistor is driven into saturation and theoutput goes low, regardless of the states of the other transistor.If all inputs are low. Then all transistor are in cutoff state and the output of the circuit goes high.

CharacteristicsIt has a fan-out of 5.Propagation delay is 25 ns.Power dissipation is 12 mw.

Noise margin for low signal input is 0.4 v.Poor noise immunity.Low speed.

Diode Transistor Logic (DTL)DTL was first commercial available IC logic family in 53/73 series.The basic circuit in the DTL logic is the NAND gate.Each input associated with one diode.The diode and resistor form an AND gate.The transistor services as a NOR gate

WorkingIf any input is low:-The corresponding diode conducts current through Vcc and resistor into the input node.The voltage at point p is equal to the input voltage + diode drop.This is a insufficient voltage for conduction of a transistor.Since the voltage at point p is 0v then the transistor is cut off state and the output is logic 1.

If all inputs are high:-The transistor is driven into saturation region.The voltage at point p is high.Hence the output is low.

Characteristics:It has fan-out of 8.It has high noise immunity.

Power dissipation is 12mw.Propagation delay is average 30ns.Noise margin is about 0.7V.

Transistor Transistor Logic (TTL)

•It can perform many digital function and have achieved the most popularity.

•TTL IC are given the numerical designation as 5400 and 7400 series

•The basic circuit of TTL with totem pole output stage is NAND gate

•TTL uses a multi-miter transistor at the input and is fast saturation logic

circuit.

•The output transistor Q3 and Q4 form a totem pole connection.

• This extra output stage is known as totem-pole stage because three output

components Q3 andQ4 and Diode are stacked on one another. This

arrangement will increase the speed the speed of operation and also increase

output current capability.

•The function of diode in this circuit prevent both Q3 and Q4 being turned

ON

simultaneously The function of diode in this circuit prevent both Q3 and Q4

being turned ON simultaneously

CharacteristicsTTL has greater speed than DTL.Less noise immunity.Power dissipation is 10mw.It has fan-in of 6 and fan-out of 10.

Propagation time delay is 5-15nsec.

Emitter Coupled Logic Gate:ECL is non saturated digital logic family.The output of ECL provides OR and NOR function.Each input is connected to the base of transistor.The circuit consists of three parts.1.differential input amplifier.2.Internal temperature and voltage compensated bias network.3.emittor follower output.The emitter output requires a pull down resistor for current flow.In this logic family we consider the logic 0 as -1.6v and logic 1 as -0.8v.

Circuit Diagram:

True Table

A B Y=A+B0 0 10 1 01 0 01 1 0

Working:A=0,B=0;If all inputs are at low level(-1.6v),the transistor are turn OFF and Q3 conducts .Then at point L the potential is 0volts is applied to the base of Q5,it is to be turn OFF.So, the output of OR gate is logic o.At the same time , the potential at point M= vcc is applied to the base of Q6,it is to be turn ON.So, the output of NOR is at logic 1.

A=0,B=0,A=0,B=1,A=1,B=0;The corresponding transistor is turned ON and Q3is turned OFF.Because its voltage needs at least 0.6v to start conduction on.An input of -0.8v causes the transistor to conduct and apply -1.6v on the remaining emitters.Therefore,Q3 is cut off. The voltage in resistor R2 flows into the base of Q5(L=Vcc) then Q5 is turned ON.The output is at logic 1.At the same time, at point M the voltage is 0v is applied to the base of the transistor Q6,it is to be turns off. So, the NOR output is logic 0.

CharacteristicsPropagation delay is very LOW(<1ns)ECL is fastest logic family.ECL circuit usually operate with –Ve supplies (+Ve terminal is connected to

ground).

3. Moore and Mealy Machines

What is (Finite State Machine)FSM?A finite state machine is a machine that has many states and has a logical way of changing from one state to the other under guiding rules.

Types of FSMWithout output (answer true or false)1. Finite State Automata

- With output2. Mealy machine

- output on transition3. Moore machine

- output on state

Mealy MachineA Mealy Machine is an FSM whose output depends on the present state as wellas the present input. In Mealy machine every transition for a particular inputsymbol has a fixed output.

State Diagram of Mealy Machine

Differences between Mealy and Moore state Machines

Advantages of Mealy and Moore state Machines• Moore machines are cheap• They are easy to use• Moore state machines are very fast• Mealy machines are reactive i.e. they have a low response time (they are fast)

Disadvantages of Mealy and Moore state Machines• Mealy state machines are expensive to produce• Number of states can become unmanageable (they become too many)Uses of Mealy and Moore state Machines• Mealy state machines are used in processors due to their property of havingmany states• Mealy state machines are also used to provide a rudimentary mathematicalmodel for cipher machines• A Moore state machine is used as a right enable in SRAM because of itsspeed.• It is used in SRAM because SRAM needs a level-sensitive control (signal hasto be asserted for an amount of time)

Conclusion• In conclusion, Mealy and Moore state machines are very important conceptsin digital design• These state machine can be used in the design of mathematical algorithms• Mealy and Moore state machines can come in both simple (having one inputand output) to complex (having many inputs and outputs) types

4. Semiconductor Memories

Memory is an essential element of today's electronics. Normally basedaround semiconductor technology, memory is used in any equipment thatuses a processor of one form or another.• Indeed as processors have become more popular and the number ofmicroprocessor controlled items has increased so has the requirement forsemiconductor memory.•An additional driver has been the fact that the software associated with theprocessors and computers has become more sophisticated and much larger,and this too has greatly increased the requirement for semiconductormemory.• In addition to this new applications such as digital cameras,PDAs and many more applications have given rise to the need to memories.• Accordingly it is not uncommon to see semiconductor memoriesof 4 Gbyteand more required for various applications

With the rapid growth in the requirement for semiconductor memories there have been a number of technologies and types of memory that have emerged.Names such as EPROM, EEPROM, Flash memory, DRAM, SRAM, SDRAM,and the very new MRAM can now be seen in the electronics literature. Each one has its own advantages and area in which it may be used.

Types of semiconductor memoryElectronic semiconductor memory can be split into two main categories, accordingto the way in which they operate:• RAM•ROM

RAMAs the names suggest, the RAM or random access memory is used or reading and writing data in any order as required. It is used for such applications as the computer or processor memory where variables and other stored and are required on a random basis. Data is stored and read many times to and from this type of memory.Types of RAM•DRAM•SRAM•SDRAM•MRAM

DRAM or Dynamic RAM is a form of random access memory. DRAM uses a capacitor to store each bit of data, and the level of charge on each capacitor determines whether that bit is a logical 1 or 0.•However these capacitors do not hold their charge indefinitely, and therefore the data needs to be refreshed periodically. As a result of this dynamic refreshing it gains its name of being a dynamic RAM.•DRAM is the form of semiconductor memory that is often used in equipment including personal computers and workstations where it forms the main RAM for thecomputer.SRAMSRAM Static Random Access Memory. This form of semiconductor memory gains its name from the fact that, unlike DRAM, the data does not need to be refreshed dynamically. It is able to support faster read and write times than DRAM (typically 10 ns against 60 ns for DRAM), and in addition its cycle time is much shorter because it does not need to pause between accesses. However it consumes more power, is lessdense and more expensive than DRAM. As a result of this it is normally used for caches, while DRAM is used as the main semiconductor memory technology

SDRAMSDRAM Synchronous DRAM. This form of semiconductor memory can run at

faster speeds than conventional DRAM.•It is synchronized to the clock of the processor and is capable of keeping two sets of memory addresses open simultaneously.•By transferring data alternately from one set of addresses, and then the other, SDRAM cuts down on the delays associated with non-synchronous RAM, which must close one address bank before opening the next.

ROM• A ROM is a form of semiconductor memory to which data is written once andthen not changed.In view of this, technologies can be used that retain the data once the power isremoved. As a result, this type of memory is widely used for storing programsand data that must survive when a computer or processor is powered down.•For example the BIOS of a computer will be stored inROM.•As the name implies, data cannot be easily written to ROM. Depending on thetechnology used in the ROM, writing the data into the ROM initially may requirespecial hardware. Although it is often possible to change the data, this gainrequires specialhardware to erase the data ready for new data to be written in.

Types Of ROMPROMEPROM

EEPROMFLASH MEMORY

PROM• PROM This stands for Programmable Read Only Memory. It is a semiconductor memory which can only have data written to it once - the data written to it is permanent.• These memories are bought in a blank format and they are programmed using a special PROM programmer. Typically a PROM will consist of an array of fuseable links some of which are "blown" during the programming process to provide the required data patternEPROM•EPROM This is an Erasablen Programmable Read Only Memory.•This form of semiconductor memory can be programmed and then erased at alater time.• This is normally achieved by exposing the silicon to ultraviolet light. To enablethis to happen there is a circular window in the package of the EPROM to enablethe light to reach the silicon of the chip.EEPROM

EEPROM This is an Electrically Erasable Programmable Read Only Memory.•Data can be written to it and it can be erased using an electrical voltage.•This is typically applied to an erase pin on the chip.•Like other types of PROM, EEPROM retains the contents of the memory even when the power is turned off. Also like other types of ROM, EEPROM is not as fast as RAM.FLASH MEMORY•Flash memory Flash memory may be considered as a development of EEPROMtechnology.•Data can be written to it and it can be erased, although only in blocks, but data can be read on an individual cell basis.•To erase and re-programme areas of the chip, programming voltages at levels that are available within electronic equipment are used.• It is also non-volatile, and this makes it particularly useful. As a result Flash memory is widely used in many applications including memory cards for digital cameras, mobile phones, computer memory sticks and many other applications.

FUZZY LOGIC

INTRODUCTION•Fuzzy logic has rapidly become one of the most successful of today's technologies for developing sophisticated control systems. The reason for which is very simple.• Fuzzy logic addresses such applications perfectly as it resembles human decision making with an ability to generate precise solutions from certain or approximate information.• It fills an important gap in engineering design methods left vacant by purely mathematical approaches (e.g. linear control design), and purely logic-based approaches (e.g. expert systems) in system design.

•While other approaches require accurateequations to model real-world behaviors,fuzzy design can accommodate theambiguities of real-world humanlanguage and logic.• It provides both an intuitive method fordescribing systems in human terms andautomates the conversion of thosesystem specifications into effectivemodels.

What do you mean by fuzzy

• Fuzzy logic is a superset of Boolean logic that has been extended to handle the concept of partial truth truth values between "completely true" and "completely false".The essential characteristics of fuzzy logic are as follows:-•In fuzzy logic, exact reasoning is viewed as a limiting case of approximate reasoning.•In fuzzy logic everything is a matter of degree.•Any logical system can be fuzzified• In fuzzy logic, knowledge is interpreted as a collection of elastic or, equivalently , fuzzy constraint on a collection of variables•The third statement hence, define Boolean logic as a subset of Fuzzy logic.

Fuzzy SetsA paradigm is a set of rules and regulations whichdefines boundaries and tells us what to do to besuccessful in solving problems within theseboundaries.• For example the use of transistors instead ofvacuum tubes is a paradigm shift - likewise thedevelopment of Fuzzy Set Theory fromconventional bivalent set•theory is a paradigm shift. Bivalent Set Theorycan be somewhat limiting if wewish to describe a 'humanistic' problemmathematically.

Fuzzy Set Operations

UnionThe membership function of theUnion of two fuzzy sets A and B withmembership functions andrespectively is defined as themaximum of the two individualmembershipfunctions. This is called the maximumcriterion.

What does it offerThe first applications of fuzzy theory were primarily industrial, such as process control for cement kilns.• Since then, the applications of Fuzzy Logic technology have virtually exploded, affecting things we use everyday.Take for example, the fuzzy washing machine .•A load of clothes in it and press start, and the machine begins to churn, automatically choosing the best cycle. The fuzzy microwave, Place chili, potatoes, or etc in a fuzzy microwave and push single button, and it cooks for the right time at the propertemperature.•The fuzzy car, maneuvers itself by following simple verbal instructions from its driver. It can even stop itself when there is an obstacle immediately ahead using sensors.

How do Fuzzy Sets different from classical Sets?In classical set theory we assume that all sets rare well-defined (or crisp), that is given any object in ouruniverse we can always say that object either is or is notthe member of a particular set.• CLASSICAL SETS•The set of people that can run a mile in 4 minutes orless.•The set of children under age seven that weigh morethan 1oo pounds.•FUZZY SETS•The set of fast runners.•The set of overweight children.

WH Y F U Z Z Y C O N T R O L ?

• Fuzzy Logic is a technique to embody human like thinking

into a control system.•A fuzzy controller is designed to emulate human deductivethinking, that is, the process people use to infer conclusionsfrom what they know.• Traditional control approach requires formal modeling of thephysical realityA Fuzzy Control System can also be described as based on fuzzy logic—a mathematical system that analyzes analog input values in terms of logical variables that take on continuous values between 0 and 1, in contrast to classical or digital logic, which operates on discrete values of either 1 or 0 (true or false respectively).

Fuzzy logic is widely used in machine control.

• The term itself inspires a certain skepticism,

sounding equivalent to "half-baked logic" or"bogus logic", but the "fuzzy" part does not refer toa lack of rigour in themethod, rather to the fact that the logic involvedcan deal with fuzzy concepts—concepts thatcannot be expressed as "true" or "false" but ratheras "partiallytrue".

m-derived Filters

Inderjeet SinghDhindsa

Limitation ofprototype Filter

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m-derived Filters

Inderjeet Singh Dhindsa

Govt. Polytechnic Ambala

06 March, 2018

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Lecture coverage

1 Limitation of prototype Filter

2 m-derived FilterT-typeΠ -type

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Limitation of Prototype Filters

The attenuation is not sharp in the stop band for k-type filters

The characteristic impedance, Z0 is a function of frequency andvaries widely in the Pass Band

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m-derived Filter (T-Section)

Let the Series arm of the section is modified by multiplying it with aconstant m. If the characteristic impedance of the section is to bemaintained same than the shunt arm impedance will be modified toZ

′

2.

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′

2.

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′

2.

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m-derived Filter (T-Section) contd...

Z0T = Z′

0T

Z 21 + Z1Z2 =

m21Z

21 +mZ1Z

′

2

Z21 + Z1Z2 =

m2Z

21 +mZ1Z

′

2

mZ1Z′

2 =(1−m

2)Z

21 − Z1Z2

Z′

2 =(1−m

2)

mZ1 +

Z2

m

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Z0T = Z′

0T√

Z 21

4+ Z1Z2 =

√

m21Z

21

4+mZ1Z

′

2

Z21 + Z1Z2 =

m2Z

21 +mZ1Z

′

2

mZ1Z′

2 =(1−m

2)Z

21 − Z1Z2

Z′

2 =(1−m

2)

mZ1 +

Z2

m

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Z0T = Z′

0T√

Z 21

4+ Z1Z2 =

√

m21Z

21

4+mZ1Z

′

2

Z21

4+ Z1Z2 =

m2Z

21

4+mZ1Z

′

2

mZ1Z′

2 =(1−m

2)Z

21 − Z1Z2

Z′

2 =(1−m

2)

mZ1 +

Z2

m

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Z0T = Z′

0T√

Z 21

4+ Z1Z2 =

√

m21Z

21

4+mZ1Z

′

2

Z21

4+ Z1Z2 =

m2Z

21

4+mZ1Z

′

2

mZ1Z′

2 =(1−m

2)

4Z

21 − Z1Z2

Z′

2 =(1−m

2)

mZ1 +

Z2

m

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Z0T = Z′

0T√

Z 21

4+ Z1Z2 =

√

m21Z

21

4+mZ1Z

′

2

Z21

4+ Z1Z2 =

m2Z

21

4+mZ1Z

′

2

mZ1Z′

2 =(1−m

2)

4Z

21 − Z1Z2

Z′

2 =(1−m

2)

4mZ1 +

Z2

m

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Z0T = Z′

0T√

Z 21

4+ Z1Z2 =

√

m21Z

21

4+mZ1Z

′

2

Z21

4+ Z1Z2 =

m2Z

21

4+mZ1Z

′

2

mZ1Z′

2 =(1−m

2)

4Z

21 − Z1Z2

Z′

2 =(1−m

2)

4mZ1 +

Z2

m

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m-derived Low Pass Filter

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m-derived Low Pass Filter m-derived High Pass Filter

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m-derived Filter (Π-Section)

Let the Shunt arm of the section be modified by dividing it with aconstant m. If the characteristic impedance of the section is to bemaintained same than the Series arm impedance will be modified toZ

′

1.

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′

1.

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′

1.

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m-derived Filter (Π-Section) contd...

Z0π = Z′

0π

Z1Z2

+ Z1

4Z2

=

√

√

√

√

√

Z′

1Z2

m

+Z

′

1

4Z2m

Z1Z2

+ Z1

4Z2

=Z

′

1Z2

m

+Z

′

1

4Z2m

Z1Z2(1 +Z

′

1Z2

m

) =Z′

1

Z2

m(1 +

Z1

Z2)

Z1Z2 +mZ1Z2Z

′

1

Z2=Z

′

1Z2

m+

Z′

1Z1Z2

mZ2

Z1Z2 +mZ1Z

′

1 =Z

′

1Z2

m+

Z′

1Z1

m

Z1Z2 =Z′

1(Z2

m+

Z1

m−

mZ1)

Z′

1 =Z1Z2

Z2

m+ Z1

4m −

mZ1

4

Z′

1 =Z1Z2

Z2

m+ (1−m2)Z1

4m

Multiplying numerator and

denominator by 4m2

1−m2

Z′

1 =(mZ1)(

4m1−m2Z2)

4m1−m2Z2 +mZ1

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Z0π = Z′

0π

√

Z1Z2

1 + Z1

4Z2

=

√

√

√

√

√

Z′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2

+ Z1

4Z2

=Z

′

1Z2

m

+Z

′

1

4Z2m

Z1Z2(1 +Z

′

1Z2

m

) =Z′

1

Z2

m(1 +

Z1

Z2)

Z1Z2 +mZ1Z2Z

′

1

Z2=Z

′

1Z2

m+

Z′

1Z1Z2

mZ2

Z1Z2 +mZ1Z

′

1 =Z

′

1Z2

m+

Z′

1Z1

m

Z1Z2 =Z′

1(Z2

m+

Z1

m−

mZ1)

Z′

1 =Z1Z2

Z2

m+ Z1

4m −

mZ1

4

Z′

1 =Z1Z2

Z2

m+ (1−m2)Z1

4m


denominator by 4m2

1−m2

Z′

1 =(mZ1)(

4m1−m2Z2)

4m1−m2Z2 +mZ1

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Z0π = Z′

0π

√

Z1Z2

1 + Z1

4Z2

=

√

√

√

√

√

Z′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2

1 + Z1

4Z2

=Z

′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2(1 +Z

′

1Z2

m

) =Z′

1

Z2

m(1 +

Z1

Z2)

Z1Z2 +mZ1Z2Z

′

1

Z2=Z

′

1Z2

m+

Z′

1Z1Z2

mZ2

Z1Z2 +mZ1Z

′

1 =Z

′

1Z2

m+

Z′

1Z1

m

Z1Z2 =Z′

1(Z2

m+

Z1

m−

mZ1)

Z′

1 =Z1Z2

Z2

m+ Z1

4m −

mZ1

4

Z′

1 =Z1Z2

Z2

m+ (1−m2)Z1

4m


denominator by 4m2

1−m2

Z′

1 =(mZ1)(

4m1−m2Z2)

4m1−m2Z2 +mZ1

m-derived Filters



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Z0π = Z′

0π

√

Z1Z2

1 + Z1

4Z2

=

√

√

√

√

√

Z′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2

1 + Z1

4Z2

=Z

′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2(1 +Z

′

1

4Z2

m

) =Z′

1

Z2

m(1 +

Z1

4Z2)

Z1Z2 +mZ1Z2Z

′

1

Z2=Z

′

1Z2

m+

Z′

1Z1Z2

mZ2

Z1Z2 +mZ1Z

′

1 =Z

′

1Z2

m+

Z′

1Z1

m

Z1Z2 =Z′

1(Z2

m+

Z1

m−

mZ1)

Z′

1 =Z1Z2

Z2

m+ Z1

4m −

mZ1

4

Z′

1 =Z1Z2

Z2

m+ (1−m2)Z1

4m


denominator by 4m2

1−m2

Z′

1 =(mZ1)(

4m1−m2Z2)

4m1−m2Z2 +mZ1

m-derived Filters



m-derived Filter

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Π -type

8/10


Z0π = Z′

0π

√

Z1Z2

1 + Z1

4Z2

=

√

√

√

√

√

Z′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2

1 + Z1

4Z2

=Z

′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2(1 +Z

′

1

4Z2

m

) =Z′

1

Z2

m(1 +

Z1

4Z2)

Z1Z2 +mZ1Z2Z

′

1

4Z2=Z

′

1Z2

m+

Z′

1Z1Z2

4mZ2

Z1Z2 +mZ1Z

′

1 =Z

′

1Z2

m+

Z′

1Z1

m

Z1Z2 =Z′

1(Z2

m+

Z1

m−

mZ1)

Z′

1 =Z1Z2

Z2

m+ Z1

4m −

mZ1

4

Z′

1 =Z1Z2

Z2

m+ (1−m2)Z1

4m


denominator by 4m2

1−m2

Z′

1 =(mZ1)(

4m1−m2Z2)

4m1−m2Z2 +mZ1

m-derived Filters



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Z0π = Z′

0π

√

Z1Z2

1 + Z1

4Z2

=

√

√

√

√

√

Z′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2

1 + Z1

4Z2

=Z

′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2(1 +Z

′

1

4Z2

m

) =Z′

1

Z2

m(1 +

Z1

4Z2)

Z1Z2 +mZ1Z2Z

′

1

4Z2=Z

′

1Z2

m+

Z′

1Z1Z2

4mZ2

Z1Z2 +mZ1Z

′

1

4=Z

′

1Z2

m+

Z′

1Z1

4m

Z1Z2 =Z′

1(Z2

m+

Z1

m−

mZ1)

Z′

1 =Z1Z2

Z2

m+ Z1

4m −

mZ1

4

Z′

1 =Z1Z2

Z2

m+ (1−m2)Z1

4m


denominator by 4m2

1−m2

Z′

1 =(mZ1)(

4m1−m2Z2)

4m1−m2Z2 +mZ1

m-derived Filters



m-derived Filter

T-type

Π -type

8/10


Z0π = Z′

0π

√

Z1Z2

1 + Z1

4Z2

=

√

√

√

√

√

Z′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2

1 + Z1

4Z2

=Z

′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2(1 +Z

′

1

4Z2

m

) =Z′

1

Z2

m(1 +

Z1

4Z2)

Z1Z2 +mZ1Z2Z

′

1

4Z2=Z

′

1Z2

m+

Z′

1Z1Z2

4mZ2

Z1Z2 +mZ1Z

′

1

4=Z

′

1Z2

m+

Z′

1Z1

4m

Z1Z2 =Z′

1(Z2

m+

Z1

4m−

mZ1

4)

Z′

1 =Z1Z2

Z2

m+ Z1

4m −

mZ1

4

Z′

1 =Z1Z2

Z2

m+ (1−m2)Z1

4m


denominator by 4m2

1−m2

Z′

1 =(mZ1)(

4m1−m2Z2)

4m1−m2Z2 +mZ1

m-derived Filters



m-derived Filter

T-type

Π -type

8/10


Z0π = Z′

0π

√

Z1Z2

1 + Z1

4Z2

=

√

√

√

√

√

Z′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2

1 + Z1

4Z2

=Z

′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2(1 +Z

′

1

4Z2

m

) =Z′

1

Z2

m(1 +

Z1

4Z2)

Z1Z2 +mZ1Z2Z

′

1

4Z2=Z

′

1Z2

m+

Z′

1Z1Z2

4mZ2

Z1Z2 +mZ1Z

′

1

4=Z

′

1Z2

m+

Z′

1Z1

4m

Z1Z2 =Z′

1(Z2

m+

Z1

4m−

mZ1

4)

Z′

1 =Z1Z2

Z2

m+ Z1

4m −

mZ1

4

Z′

1 =Z1Z2

Z2

m+ (1−m2)Z1

4m


denominator by 4m2

1−m2

Z′

1 =(mZ1)(

4m1−m2Z2)

4m1−m2Z2 +mZ1

m-derived Filters



m-derived Filter

T-type

Π -type

8/10


Z0π = Z′

0π

√

Z1Z2

1 + Z1

4Z2

=

√

√

√

√

√

Z′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2

1 + Z1

4Z2

=Z

′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2(1 +Z

′

1

4Z2

m

) =Z′

1

Z2

m(1 +

Z1

4Z2)

Z1Z2 +mZ1Z2Z

′

1

4Z2=Z

′

1Z2

m+

Z′

1Z1Z2

4mZ2

Z1Z2 +mZ1Z

′

1

4=Z

′

1Z2

m+

Z′

1Z1

4m

Z1Z2 =Z′

1(Z2

m+

Z1

4m−

mZ1

4)

Z′

1 =Z1Z2

Z2

m+ Z1

4m −

mZ1

4

Z′

1 =Z1Z2

Z2

m+ (1−m2)Z1

4m


denominator by 4m2

1−m2

Z′

1 =(mZ1)(

4m1−m2Z2)

4m1−m2Z2 +mZ1

m-derived Filters



m-derived Filter

T-type

Π -type

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Z0π = Z′

0π

√

Z1Z2

1 + Z1

4Z2

=

√

√

√

√

√

Z′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2

1 + Z1

4Z2

=Z

′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2(1 +Z

′

1

4Z2

m

) =Z′

1

Z2

m(1 +

Z1

4Z2)

Z1Z2 +mZ1Z2Z

′

1

4Z2=Z

′

1Z2

m+

Z′

1Z1Z2

4mZ2

Z1Z2 +mZ1Z

′

1

4=Z

′

1Z2

m+

Z′

1Z1

4m

Z1Z2 =Z′

1(Z2

m+

Z1

4m−

mZ1

4)

Z′

1 =Z1Z2

Z2

m+ Z1

4m −

mZ1

4

Z′

1 =Z1Z2

Z2

m+ (1−m2)Z1

4m


denominator by 4m2

1−m2

Z′

1 =(mZ1)(

4m1−m2Z2)

4m1−m2Z2 +mZ1

m-derived Filters



m-derived Filter

T-type

Π -type

8/10


Z0π = Z′

0π

√

Z1Z2

1 + Z1

4Z2

=

√

√

√

√

√

Z′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2

1 + Z1

4Z2

=Z

′

1Z2

m

1 +Z

′

1

4Z2m

Z1Z2(1 +Z

′

1

4Z2

m

) =Z′

1

Z2

m(1 +

Z1

4Z2)

Z1Z2 +mZ1Z2Z

′

1

4Z2=Z

′

1Z2

m+

Z′

1Z1Z2

4mZ2

Z1Z2 +mZ1Z

′

1

4=Z

′

1Z2

m+

Z′

1Z1

4m

Z1Z2 =Z′

1(Z2

m+

Z1

4m−

mZ1

4)

Z′

1 =Z1Z2

Z2

m+ Z1

4m −

mZ1

4

Z′

1 =Z1Z2

Z2

m+ (1−m2)Z1

4m


denominator by 4m2

1−m2

Z′

1 =(mZ1)(

4m1−m2Z2)

4m1−m2Z2 +mZ1

m-derived Filters



m-derived Filter

T-type

Π -type

9/10

m-derived Filter(Π - Section) contd...

m-derived Filters



m-derived Filter

T-type

Π -type

10/10

T Lines

I.S.Dhindsa

Introduction

Classification

Application ofTLines

Equivalent Circuit

PrimaryConstants

SecondaryConstants

1/8

Transmission Lines

Inderjeet Singh Dhindsa

Govt. Polytechnic Ambala

March 20, 2018

T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

2/8

Transmission Lines

The Transmission Line is a conductive method of guidingelectrical energy from one place to another

They are used as a link between a transmitter and/ or receiver

Transmission lines not only transmit energy, but also act ascircuit elements like inductor , capacitors, resonant circuit etc

T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

3/8

Types of Transmission lines

Basically there are four types ofTransmission Lines

1 Parallel wire type

Coaxial Cable

Wave Guide

Optical Fiber

Optical fiber is a flexible,transparent fiber made ofglass (silica) or plastic ofthickness slightly morethan that of a human hairInformation transmitted aslight signalAdvatages: Lowattenuation, Highimmunity to EMI

T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

3/8




Two closely spaced parallelwires separated by air ordielectricDistance between the wiresis 2 to 6 inchAdvantage : Easy toconstructDisadvantage :Highradiation losses, pick upnoise

Coaxial Cable

Wave Guide

Optical Fiber


T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

3/8




2 Coaxial Cable

These cables has an innerconductor surrounded by atubular insulating layer,surrounded by a tubularconducting shield usually awire meshMany coaxial cables alsohave an insulating outersheath or jacketAdvantages: Widebandwidth and Low errorratesDisadvantages : Highinstallation cost

Wave Guide

Optical Fiber


T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

3/8




2 Coaxial Cable

3 Wave Guide

These are hollowconducting metallic tubesof uniform cross-sectionUsed in UHF andMicrowave frequency signalWave guides are passivemicrowave devices, whichfunctions as High PassFilter (HPF) for microwavefrequenciesAdvantages : High powerhandling capacity

Optical Fiber


T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

3/8




2 Coaxial Cable

3 Wave Guide

4 Optical Fiber


T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

4/8

Applications of Transmission Lines

1 To transmit electric energy

2 To transmit communication signal from transmitter to receiver

3 To work as circuit element at high frequencies

4 For impedance matching

T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

5/8

Equivalent Circuit of Transmission Line

Consider a long line consisting of 2parallel uniform conductor carryingcurrent

There is a magnetic field around theconductors and voltage drop alongthem

Voltage applied across the conduct rproduce an electric field between theconductors and charge on them

T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

5/8




Voltage applied across the conduct rproduce an electric field between theconductors and charge on them

T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

5/8




Voltage applied across the conductorproduce an electric field between theconductors and charge on them

T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

5/8




Voltage applied across the conductorproduce an electric field between theconductors and charge on them

T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

6/8

Primary constant of Transmission Line

The four line parameters R,L,C and G are called Primary Constant ofTransmission Line

1 Resistance R is defined as loop resistance per unit length ofline.Its unit is Ω/Km.

2 Inductance L is defined as loop inductance per unit length. Itsunit is H/Km.

3 Conductance G is defined as shunt conductance between the twowires per unit length. Its unit is /Km.

4 Capacitance C is defined as shunt capacitance between the twowires per unit length. Its unit is F/Km.

T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

7/8

Secondary constant of Transmission Line

The Secondary constants of transmission lines are derived fromPrimary Constant R,L,C and G of Transmission Line

1 Characteristics Impedance (Z0)

2 Propagation Constant (γ)

T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

7/8



1 Characteristics Impedance (Z0)

2 Propagation Constant (γ)

Characteristic Impedance Z0

The characteristic impedance Z0 of a uniform transmission line is theratio of the amplitudes of voltage and current of a single wavepropagating along the line; that is, a wave traveling in one directionin the absence of reflections in the other direction.

Z0 =√

R+jωLG+jωL

T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

7/8



1 Characteristics Impedance (Z0)2 Propagation Constant (γ)

Propagation Constant γ

γ =√

(R + jωL)(G + jωL)

γ is a complex quantity having real and imaginary part.

γ =α+ jβ

α =

√

1

2[(RG − ω2LC ) +

√

(R + jωL)(G + jωL)]

β =

√

1

2[(ω2LC − RG )−

√

(R + jωL)(G + jωL)]

T Lines

I.S.Dhindsa

Introduction

Classification


Equivalent Circuit

PrimaryConstants

SecondaryConstants

8/8

E.D.M.

1. ENTREPRENEURSHIP

MEANING OF AN ENTREPRENEUR

Webster dictionary an entrepreneur is defined as "an individualwho forecasts future demand for a product or service and arrangesa business enterprise to respond to their demand.”

QUALITIES OF AN ENTREPRENEURInitiator Opportunity seekerCalculated risk takerInformation seekerPersistentCommitted to workEfficiency loverQuality consciousProper planner

Self-confident

AssertiveEfficient supervisorSound technical know-howEfficient financial managerGood human relationsInnovativeness LeadershipSystematic approachSaving habitCourageous

CONCEPT/MEANING OF ENTREPRENEURSHIP

The word 'entrepreneurship' has been derived from a French root which means 'to undertake’

NEED OF ENTREPRENEURSHIP Capital formation Improvement in per capita incomeDevelopment of entrepreneurial cultureEconomic independenceBackward and forward linkages

BASIC COMPONENTS OF ENTREPRENEURSHIPThe various components required for an enterprise can also be grouped in the following ways :Technology (Men, Methods, Management)finance (Money, Material. Machine)Sales and marketing (Market)

TYPES OF ENTREPRENEURS

Innovative entrepreneurs : An innovative entrepreneur is one whointroduces new method of production, discovers new goods, penetratesinto new markets. Hence such entrepreneurs come up with somethingnew and avoid the already beaten trackImitative entrepreneurs : These entrepreneurs follow the path ofinnovative entrepreneurs. Imitative entrepreneurs do not innovate thechanges themselves, they only imitate techniques and technologyinnovated by others.Fabian entrepreneurs : These entrepreneurs are very cautious inexperimenting any change in their enterprises. They adopt changes onlywhen they feel that their survival is not possible without this change.Hence such type of entrepreneurs avoid changes till maximum possible.Drone entrepreneurs : These entrepreneurs are not ready to makechanges in their existing2 production methods even after suffering greatlosses.

BARRIERS IN ENTREPRENEURSHIP orCAUSES OF ENTREPRENEURIAL FAILURE

Management factorsIncompetencyInexperience in lineInexperience in management

Production factorsPoor raw materialsLack of technical knowhowLack of production planning and controlFrequent power cutsFrequent mechanical breakdownLabour problemsInsufficient quality control Wastage in materialHigh rate of rejection

High fixed costHeavy investment in land and building.High administrative and other overhead expenditure.Market borrowing at high interest.

Marketing problemsCompetition from larger and already established enterprises in the same lineLow quality of finished goods Recess ionFinancial problemsSale on creditUtilising short term funds for long term uses

SOLE PROPRIETORSHIPSole proprietorship or individual proprietorship is the simplest and the oldestform of business organization.According to Wheeler," the sole proprietorship is that form of businessorganization which is owned and controlled by a single individual. He receivesall the profits and bears all the risks in the success or failure of the enterprise

Salient features of sole proprietorship :(t) Single ownership (ii) One man controlUnlimited liability (iv) Undivided risk(v) No separate legal entity of the firm

Merits of sole proprietorship :( One man control i.e. independent controlEase of formationQuick decisions

Demerits of sole proprietorship :Limited fundsLimited scope of expansionthe capacity of a single person, a group of persons have to join hands together andsupply the required capital and skills.According to Partnership Act, 1932" partnership is the relation between personswho 'have agreed to share the profits of a business carried on by all or anyone, ofthem acting for all“Characteristics of partnership firms:Two or more personAgreement-written or oralLawful business(Sharing of profitsUnlimited liabilityNo separate legal entity of the firmRestriction on transfer of interestREGISTRATION OF FIRMSA partnership firms can be registered at any time by filing a statement in theprescribed form. The form should be duly signed by all the partners. It should besent to Registrar of firms along with the prescribed fee. On receipt of the statementand the fees, the Registrar makes an entry in Register of firms. The firm isconsidered to be registered when the entry is made. The Registrar issues aCertificate of Registration.

KHADI AND VILLAGE INDUSTRIES COMMISSION (KVIC)Khadi and Village Industries Commission was established in 1953 with theprimary objective of developing khadi and village industries and improving ruralemployment opportunities.KVIC’s policies and programmes are executed through State Khadi and VillageIndustries Boards, institutions registered under the Societies Registration Act,1960 and Industrial Cooperative Societies registered under State CooperativeSocieties ActTECHNICAL CONSULTANCY ORGANISATIONS (TCOs)The network of TCOs was established by the all India financial institutions incollaboration with state level financial institutions in order to provideconsultancy services to entrepreneurs setting up small and medium scale units.The following functions are performed by TCOs :To prepare project reports and feasibility4 study.To undertake industrial potential surveys.To identify potential entrepreneurs and provide them technical andmanagement assistance.To undertake market research and surveys for specific products.To supervise the project and render5 technical and administrative assistancewherever necessary.To undertake export consultancy for export-oriented projects.To conduct entrepreneurship development programmes.

SCIENCE ANTECHNOLOGY ENTREPRENEUR PARKS (STEP)

A technology park is an area where applied research on high techprojects is conducted with the collaboration of companies, universitiesand technological institutions.A conventional science and technology park was set up by the BirlaInstitute of Scientific Research (BISR) in 1972 at BIT Ranchi.

TECHNOLOGY BUSINESS INCUBATOR (TBI)Technology business incubators are a powerful economic developmenttool.

2. MARKET SURVEY AND OPPORTUNITY

IDENTIFICATION

SCANNING OF BUSINESS ENVIRONMENTThere are a number of common approaches for such type of analysis. One of the most important analysis is PESTEL analysis.

Political factorsTaxation policyTrade regulationsGovernment stabilityUnemployment policy

Economical factorsInflation rateGrowth in spending powerRecession or boomCustomer liquidations

Socio-eultural factorsLanguageReligionEducationLiteracyLiteracyTechnological factorsInternetE-commerceElectronic mediaResearch and developmentRate of technological change Waste disposalEnergy consumptionPollution monitoring

DATA COLLECTION FOR SETTING UP SMALL VENTURESThe data to be collected for setting up new ventures may be classified into followingheads :Raw materials dataMachinery and equipments dataMarket dataFinancial dataPersonnel dataGeneral data

Raw materials data :Name of the major suppliers of the raw materials needed for the project.Materials to be imported, if any. Govt policies regarding the import of this material.Prices and availability of raw materials in the last few years.

Machinery and equipments data :Who are the manufactures/suppliers of the machinery needed for the project?What are the specifications of different brands of machineries available in themarket?What are the terms of supply?What is the normal repair and maintenance cost?

Market data :Collect the data from the existing manufactures/competitors of the proposed product regarding the following :Range of productsInstalled and utilized capacity of their unitsPrices of their productsTheir terms of businessCollect the following data regarding the consumers :What is the requirement of an average consumer?What are the present sources of supplyWhether he is satisfied with the present products?What are the preferences of the customer in case of your product

Financial data :Approximate financial requirements of the proposed unit.Prevailing rates of interest on term loan and working capital loan offered by different financial institutions.Financial incentives available in the present case (id) Financing patternSources of term loan and working capital loan

Personnel data :Total manpower needed for the proposed unitCategory wise requirement of manpower and their qualifications and skillsrequiredAre the key personnel like engineers/technical personnel/supervisors easilyavailable as per the requirement of the proposed project?What are the prevailing wage and salary rates?

ASSESSMENT OF DEMAND AND SUPPLY IN POTENTIAL AREAS OFGROWTH (SALES FORECASTING)The entrepreneur is required to know the demand of the product likely to bemanufactured. In other words, he must know the estimate of sale potential of thefirm in future. All manufacturing units are based on the sale forecasts. Thisforecast helps the management in determining as to how much will be theturnover, how much profits to manufacture and what shall be the requirement ofmen, machine and money.IMPORTANCE OF ASSESSMENT OF DEMAND & SUPPLYSales forecasting is a very important function for manufacturing concern, since itis useful in following ways :(i) It helps to determine production volumes considering availability of facilitieslike equipment, capital, manpower etc.(ii) It helps in taking decisions about the plant expansion and changes inproduction schedule or should it divert1 its resources for manufacturing otherproducts.

FACTORS FOR SALES FORECASTINGFollowing factors should be considered while making the sales forecast :CompetitionChanges in technologyGovernment policiesFactors related to the concernMETHODS USED FOR FORECASTING THE DEMANDFollowing methods are generally used for forecasting of sales :Customer’s viewsSalesmen’s opinionTrends projectionsIDENTIFYING BUSINESS OPPORTUNITYTo establish an enterprise, one needs a situation in which his ideas can beconverted into project and profitsThere must be a good demand for the product he is going to design :He should analyse the gap between the demand and supply of the product intoconsideration. The demand must be sufficiently higher than the supply. Not onlythe present demand and supply should be studied but also the future demand andsupply position has to be projected. While analyzing the demand and supplyposition, the entrepreneur has to take into account the possibilities of establishinganother new units and inter-regional flow of the goods.

There must be a good returns on the investment : If the rate of returns onthe investment is not attractive, the entrepreneur should not go ahead to explore1

the opportunity even if there is a good scope for the product. The rate of returnmust be higher in comparison to other alternatives available. The rate of return onthe investment should also be such that it covers the remuneration of theentrepreneur, interest on the loans and something extra to repay the cost ofproject so that the entrepreneur will be able to recover the entire cost of theproject in near future.CONSIDERATIONS IN PRODUCT SELECTIONThe product to be selected must meet one of the following criteria :The product is the pioneer in the market and will satisfy a presently unservedneed.The product is such that for which there is already more demand than the existingsupply in the marketThe product is such that which can successfully compete with existing similarproducts in the market due to its improved3 design or lower price etc.

The following factors must be considered in product selection :Present market : The size of the presently available market is the main decidingfactor in the product selection. Estimates of the number of potential customers andtheir expected individual capacity to consume, gives the sales estimate of theproduct in consideration. The presence of similar products in the market and theirquality and price also must be considered.

Scope of growth of market : There should be a prospect for rapid growth inthe market. Projected1 increase in number of potential customers, increase inneed, favorable economic trends must be taken into account while selecting aproduct for manufacturing.

Costs : The cost of production and distribution must permit an acceptable profitwhen the product is priced competitively. Costs of raw materials, labour costs,distribution costs, after sale-service costs etc. must be considered before taking afinal decision on product selection.

Availability of main production factors : Production factors such as rawmaterials, water, power, fuel and skilled labour should be examined to ensure theiravailability comfortably and at competitive rates.

Risks : It is impossible to look into the future with certainty2. While it may bedifficult or impossible to predict the future, we can examine with considerableconfidence the possible effect of unfavourable future events on the product to bemanufactured. The possible risks are technological risks, competition, marketstability, quality and reliability4 risks, predictability of demand, seasonal demand,change in Govt, policies towards the product etc.

3. PROJECT REPORT PREPARATION

SIGNIFICANCE OF A PROJECT REPORTor

NEED OF A PROJECT REPORT1. The project report is like a roadmap.2. It helps the entrepreneur in getting provisional°/permanent registration of

the project from the district industries centre.3. It helps in allotment of industrial plot or shed for the project from state

industrial development corporation.4. It helps the entrepreneur in obtaining working capital loan or term loan

from banks/state financial corporation/other financial institutions.CONTENTS OF A PROJECT REPORT1. Objective and scope of the report2. Promoter’s profile3. Location4. Land arid building5. Plant and machinery6. Production process7. Other utilities8. Raw materials9. Market potential10.Personnel

PRELIMINARY PROJECT REPORT (P.P.R.)A preliminary project report is a brief summary of a project describing theexpected inputs and outputs like finance, manpower, machinery, materials,technology, expenses, production, sales and profits etc. of a project before theproject is actually implemented.

DETAILED PROJECT REPORTDetailed project report is nothing but a detailed elaboration' of each and everyinformation and estimates mentioned in the preliminary project report. Whilepreparing a Detailed Project Report (D.P.R.) the entrepreneur may take thehelp of experts to do the job. Preparation of the DPR requires a lot of time andhence it is a voluminous work. Detailed analysis of each and every item isnecessary in a D.P.R.

PROJECT APPRAISALThe exercise of project appraisal simply means the assessment of a project interms of its economic, technical, social and financial viability. Simply speaking,project appraisal means the assessment of a project.

STAGES OF PROJECT APPRAISAL

1. Economical Analysis2. Financial Analysis3. Technical Feasibility4. Managerial Competence5. Market/Commercial Analysis

ECONOMICAL ANALYSIS

FINANCIAL ANALYSIS

TECHNICAL FEASIBILITYneed to be covered in the report:1.Process technology2. Economic size of the project3. Technical know-how and consultancy

MANAGERIAL COMPETENCEMARKET/COMMERCIAL ANALYSISmethods to estimate the demand for a product are as follows :(a) Opinion poll method(b) Life cycle segmentation analysis

This may be attempted with the help of either a complete survey of allcustomers or by selecting a few out of the relevant populationcycle segmentation analysis, the product life cycle passes throughfollowing five stages :1. Introduction2. Growth3. Maturity4. Saturation5. Decline

4.INTRODUCTION TO MANAGEMENT

MANAGEMENT

Management is knowing exactly what you want men to do and then seeingthat they do it in the best and cheapest way.

NEED OF MANAGEMENTorIMPORTANCE OF MANAGEMENT

1. Tough competition in the market2. Production efficiency3. Industrial peace4. Limited financial resources5. Expansion of industries6. Complexity of industries

FUNCTIONS OF MANAGEMENT1.Planning2.Organising3.Staffing4.Co-ordinating5.Directing6.Motivating7.Controlling

HIERARCHICAL MANAGEMENT

STRUCTURE

1. Top level management

2. Middle level management

3. Lower level management

DEPARTMENTATION

Departmentation involves the dividing and grouping of

the work to be done in an enterprise.

To perform various functions, different departments are

established. These are as follows :

1. Personnel department.

2. Finance department.

3. Marketing department.

4. Production department,.

5. Purchase department.

LEADERSHIP

Leadership is the ability to persuade others to seek defined

objectives enthusiastically. It is the human factor which binds

a group together and motivates it towards goals.

NEED OF LEADERSHIP

To motivate employees

To create confidence

To build morale

To define objectives of organisation

To create a team-spirit

For efficient and economical working

To handle difficult situations

To develop a sense of participation2 among workers

QUALITIES/CHARACTERISTICS OF A GOOD LEADER

Emotional stability

Human relations

Motivating skills

Communication skills

Technical skills

Objectivity

Social skills

Decisiveness

Sincerity, honesty and integrity

Intelligence

TYPES/ STYLES OF LEADERSHIP

Autocratic leadership (Authoritarian)

Democratic leadership (Participative)

Laisse-faire (Free-rein)

MOTIVATION

The term 'motivation' has been derived from the word 'motive'. Motive may

be defined as an inner state of our mind that moves or activates or energises

and directs our behaviour towards our goals. Motives are expressions of a

person's goals or needs. They give direction to human behaviour to achieve

goals or fulfil needs.

CHARACTERISTICS OF MOTIVATION

Motivation is a psychological concept which is inherent in every person.

Person in totality, not in part, is motivated.

Motivation is an unending process. Needs of a man are unending. Needs

instigate6motivation.

Motivation is the strength of work which leads to do or not to do a work.

Motivation is different from mental strength.

Motivation causes good directed behaviour.

Motivation is derived from objectives or aims.

IMPORTANCE/NEED OF MOTIVATION IN AN

ORGANISATION

High performance level

Low employee turnover and less absenteeism

Acceptance of organizational changes

Good industrial relations

Less number of complaints and grievances

TYPES OF MOTIVATION

Positive motivation or Negative motivation

Extrinsic5 motivation or Intrinsic5 motivation

Financial motivation or Non-financial motivation

METHODS OF IMPROVING MOTIVATION

Financial incentives

Non-financial incentives

Cell Structure and Function

Cells

• Smallest living unit

• Most are microscopic

Discovery of Cells

• Robert Hooke (mid-1600s)

– Observed sliver of cork

– Saw “row of empty boxes”– Coined the term cell

Cell theory

• (1839)Theodor Schwann & Matthias Schleiden

“ all living things are made of cells”

• (50 yrs. later) Rudolf Virchow

“all cells come from cells”

Principles of Cell Theory

• All living things are made of cells

• Smallest living unit of structure and function of all organisms is the cell

• All cells arise from preexisting cells

(this principle discarded the idea of

spontaneous generation)

Cell Size

Cells Have Large Surface

Area-to-Volume Ratio

Characteristics of All Cells

• A surrounding membrane

• Protoplasm – cell contents in thick fluid

• Organelles – structures for cell function

• Control center with DNA

Cell Types

• Prokaryotic

• Eukaryotic

Prokaryotic Cells

• First cell type on earth

• Cell type of Bacteria and Archaea

Prokaryotic Cells

• No membrane bound nucleus

• Nucleoid = region of DNA concentration

• Organelles not bound by membranes

Eukaryotic Cells• Nucleus bound by membrane

• Include fungi, protists, plant, and animal cells

• Possess many organelles

Protozoan

Representative Animal Cell

Representative Plant Cell

Organelles

• Cellular machinery

• Two general kinds

– Derived from membranes

– Bacteria-like organelles

Bacteria-Like Organelles

• Derived from symbiotic bacteria

• Ancient association

• Endosymbiotic theory

– Evolution of modern cells from cells & symbiotic bacteria

Plasma Membrane

• Contains cell contents

• Double layer of phospholipids & proteins

Phospholipids

• Polar

– Hydrophylic head

– Hydrophobic tail

• Interacts with water

Movement Across the Plasma Membrane

• A few molecules move freely

– Water, Carbon dioxide, Ammonia, Oxygen

• Carrier proteins transport some molecules

– Proteins embedded in lipid bilayer

– Fluid mosaic model – describes fluid nature of a lipid bilayer with proteins

Membrane Proteins

1. Channels or transporters

– Move molecules in one direction

2. Receptors

– Recognize certain chemicals

Membrane Proteins

3. Glycoproteins

– Identify cell type

4. Enzymes

– Catalyze production of substances

BIOMEDICALTRANSDUCERS

Transducers

Transducer

a device that converts primary form of energy into other

different energy form only for measurement purposes.

Primary Energy Forms: mechanical, thermal, electromagnetic,

optical, chemical, etc.

Sensor

It is a wide term which covers almost everything from human eye

to trigger of a pistol.

Senses the change in parameter(specific).

Classification of Transducers

Active & Passive Transducers

Absolute & Relative Transducers

Direct & Complex Transducers

Analog & Digital Transducers

Primary & secondary Transducers

On the basis of principle used

Active vs Passive Transducers

Active Transducers:Add energy to the measurement environment as part of the measurement process.

Requires external power supply.Strain gauge, potentiometer & etc.

Passive Transducers :Do not add energy as part of the measurement process but may remove energy in their operation.

Does not require external power supply

Thermocouple, photo-voltaic cell & etc.

ANALOG & DIGITAL

TRANSDUCERS

ANALOG TRANSDUCER-

The transducers which convert the input quantity into an

analog output which is a continuous function of time.

DIGITAL TRANSDUCERS-

The transducers which convert the input quantity into digital

form means in the form of pulses.

PRIMARY vs SECONDARY

TRANSDUCERS

PRIMARY TRANSDUCERS - Some transducers contain

the mechanical as well as electrical device. The

mechanical device converts the physical quantity

to be measured into a mechanical signal. Such mechanical

device are called as the primary transducers.

SECONDARY TRANSDUCERS - The electrical device

then convert this mechanical signal into a corresponding

electrical signal. Such electrical device are known as

secondary transducers

CLASSIFICATION ON THE BASIS OF PRINCIPLE USED

Capacitive Inductive

Resistive

Electromagnetic

Piezoelectric

Photoconductive

Photovoltaic

Transducers for Physiological Variable

Measurements

•

• A variable is any quantity whose value changes with time. A variable associated with the physiological processes of the body is known as a physiological variable.

Physiological variables occur in many forms: as ionic potential,

mechanical movements, hydraulic pressure ,flows and body

temperature etc.

Different transducers are used for different physiological

variables.

Electrodes:Electrodes convert ionic potential into electrical signals.

Used for EEG, ECG, EMG, ERG and EOG etc.

Different types of Electrodes are:

1) Surface Electrodes(no. Of muscles)

These electrodes are used to obtain bioelectric potentials from the surface of the

body.

2) Needle electrodes(specific to a muscle)

These electrodes are inserted into body to obtain localized measurement of

potentials from a specific muscle.

3) Microelectrodes(cellular level record)

Electrodes have tips sufficiently small to penetrate a single cell in order to

obtain readings from within cell.

Electrical Activity

Measurement

Working of Electrodes: When metal electrodes come in contact with electrolyte then ion-electron

exchange takes place as a result of electro-chemical reaction.

One cation M+

out of the electrolyteOne atom M out of the metalis oxidized to form becomes one neutral

atom Mone cation M+ and taking off one free giving off one free electronelectron e- to the from the metal metal.

Electrical Activity

Measurement(cont.)

Half-cell potentialOxidation and reduction processes take place when metal comes in contact with

Electrolyte .

Net current flow is zero but there exists a potential difference depends upon the

position of equilibrium and concentration of ions. That p.d. is known as half-cell

potential.

Over-potentialIf there is a current between the electrode and electrolyte then half-cell

potential altered due to polarization is known as over-potential.

Electrical Activity

Measurement(cont.)

Electrical Activity

Measurement(cont.)

Types of Electrodes: Perfectly Polarizable Electrodes

- only displacement current, electrode behave like a capacitor

example: noble metals like platinum Pt

Perfectly Non-Polarizable electrode

- current passes freely across interface,

- no overpotential

examples:

- silver/silver chloride (Ag/AgCl),

- mercury/mercurous chloride

Blood pressure is an important signal in determining the

functional integrity of the cardiovascular system. Scientists and

physicians have been interested in blood pressure measurement

for a long time.

Blood Pressure

• Blood pressure measurement techniques are generally put into two

broad classes:

1) DIRECT TECHNIQUES

•Direct techniques of blood pressure measurement, which are also

known as invasive techniques, involve a catheter to be inserted into

the vascular system.

2) INDIRECT TECHNIQUES

•The indirect techniques are non-invasive, with improved patient

comfort and safety, but at the expense of accuracy.

Blood Pressure Measurement

Strain GaugesResistance is related to length and area of cross-section of theresistor and resistivity of the material asBy taking logarithms and differentiating both sides, the equation becomes

Dimensional

piezoresistanc e

Strain gage component can be related by poisson’s ratio as

Transducers for Blood Pressure

Measurement

Strain GaugesGage Factor of a strain gage

Think of this as a Transfer Function!

Input is strain

Output is dR

G is a measure of sensitivity

Put mercury strain gauge around an arm or chest to measure force of muscle contraction or respiration, respectively

Used in prosthesis or neonatal apnea detection, respectively


Measurement(cont.)

Strain Gauges


Measurement(cont.)

An inductor is basically a coil of wire over a “core” (usually ferrous)

It responds to electric or magnetic fields

A transformer is made of at least two coils wound over the core: one is primary and another is secondary

Primary Secondary Displacement Sensor

Inductors and tranformers work only for ac signals

Inductive Pressure Sensors ( LVDT)


Measurement(cont.)

Capacitive Pressure Sensors

When there is difference in P1 & P2 then diaphragm moves toward low pressure side and accordingly capacitance varies. So, capacitance becomes function of pressure and that pressure can be measured by using bridge ckt.

It can be used for blood pressure measurent.


Measurement(cont.)

Capacitive Pressure Sensors

Pressure

An example of a capacitive sensor is a pressure sensor.In parts a, the thin sensor diaphragm remains parallel to the fixed electrode and in part b, the diaphragm deflects under applied pressure resulting in capacitance change


Measurement(cont.)


Measurement(cont.)

Fibre-optic pressure sensor

The other pressure sensing approach, characterized by a diaphragm in front of the fibre optic link, is based on the light intensity modulation of the reflected light caused by the pressure-induced position of the diaphragm.

Blood Flow

A measure of the velocity of blood in a major vessel. In a

vessel of known diameter , this can be calibrated as flow and

is most successful accomplished in arterial vessels. Used to

estimate heart output and circulation. Requires exposure of

the vessel. Flow transducer surrounds vessel. Methods of

measurement include

Electro-magnetic

Ultrasonic principles

Fibre-optic laser Dopplerflowmetry

L

e uB dL

0

For uniform B and uniform velocity profile

u, the induced emf is e=BLu. Flow can be

obtained by multiplying the blood velocity u

with the vessel cross section A.

Electromagnetic Flow metersBased on Faraday’s law of induction that a conductor that moves

through a uniform magnetic field, or a stationary conductor placed in a

varying magnetic field generates e m f on the conductor:

When blood flows in the vessel with velocity u and passes through

the magnetic field B, the induced emf measured at the electrodes:

Blood Flow Measurement

Electromagnetic Flow meter Probes

• Comes in 1 mm increments for1 ~ 24 mm diameter blood vessels

• Individual probes cost $500 each

• Only used with arteries, not veins,as collapsed veins during diastolelose contact with the electrodes

• Needless to say, this is an INVASIVE measurement!!!

• A major advantage is that it can measure instantaneous blood flow, not just average flow.

Blood FlowMeasurement(cont.)

Ultrasonic Flow meters

Based on the principle of measuring the time it takes for an

acoustic wave launched from a transducer to bounce off red

blood cells and reflect back to the receiver.

All UT transducers, whether used for flowmeter or other

applications, invariably consists of a piezoelectric material,

which generates an acoustic (mechanical) wave when excited

by an electrical force (the converse is also true)

UT transducers are typically used with a gel that fills the air

gaps between the transducer and the object examined


Ultrasonic Flow meters

The Doppler blood-flow measurement

Doppler blood flow detectors operate by means of continuous sinusoidal excitation. The frequency difference calibrated for flow velocity can be displayed or transformed by a loudspeaker into an audio output.



Fibre-optic laser Doppler flow metry

The basic scheme of fibre-optic laser Doppler flow metry is illustrated in figure. The light of a He–Ne laser is guided by an optical fibre probe to the tissue or vascular network being studied. The light is diffusely scattered and partially absorbed within the illuminated volume. Light hitting moving blood cells undergoes a slight Doppler shift. The blood flow rate is derived by the spectrum-analysis of the back-scattered signal, which presents aflow-dependent Doppler-shifted frequency.

Temperature

Systematic Temperature:

A measure of the basic temperature of the complete

organism. Measured by thermometer, oral thermistor

probe. Skin Temperature:

Measurement of the skin temperature at a specific part of

body surface. Measured by thermistors placed at surface

of the skin , infrared thermometer or thermograph.

Thermistors are made from

semiconductor material.

Generally, they have a negative temperature coefficient (NTC), that is NTC thermistors are most commonly used.

Ro is the resistance at a reference point (in the limit, absolute 0).

Thermistor

Temperature Measurement

Thermocouples

Seebeck Effect

When a pair of dissimilar metals are joined at one end, and there is a temperaturedifference between the joined ends and the open ends, thermal emf is generated,which can be measured in the open ends.

This forms the basis of thermocouples.

In a bimetallic strip, each metal has a different thermal coefficient…this results in electromagnetic force/emf or bending of the metals.

Temperature Measurement(cont.)

Fiber Optics

Most of the light is trapped in the core, but if the cladding is temperature sensitive (e.g. due to expansion), it might allow some light to leak through.

-> hence the amount of light transmitted would be proportional to temperature

-> since you are measuring small changes in light level, this sensor is exquisitely sensitive



Liquid-in-glass Thermometer

A common form of mercury-in-glass is a solid-stem glass thermometer shown in figure. When bulb comes in contact with temperature then mercury expands and gives direct value on main scale.

Respiration sensors

The primary function of the respiratory system are to supply oxygen to the

tissues and remove carbon-dioxide from tissues. Several types of transducers

have been developed for measurement of respiration rate.

1) Strain Gauge type chest transducer

The transducer is held by an elastic band which goes around the chest. The

respiratory movements result in resistance change of the strain gauge element

connected in Wheatstone bridge. The bridge output varies with chest

expansion and yields signals corresponding to respiratory activity.

2) Thermistor

Air is warmed during its passage through the lungs and there is a detectable

temperature difference between inspired and expired air. Temperature change

can be measured by thermistor and it gives rate of change of resistance and

hence calibrated in terms of respiration rate.

Pulsesensors

Heart rate measurement is one of the very important parameters of

the human cardiovascular system. The heart rate of a healthy adult

at rest is around 72 beats per minute (bpm).

Basically, the device consists of an infrared transmitter LED and an

infrared sensor photo-transistor. The transmitter-sensor pair is

clipped on one of the fingers of the subject. The LED emits infrared

light to the finger of the subject. The photo-transistor detects this

light beam and measures the change of blood volume through the

finger artery. This signal, which is in the form of pulses is then

amplified and filtered suitably and is fed to a low-cost

microcontroller for analysis and display

Pulse Sensor (cont.)

The microcontroller counts the number of pulses over a fixed time interval and thus obtains the heart rate of the subject. Several such readings are

obtained over a known period of time and the results are averaged to give a

more accurate reading of the heart rate. The calculated heart rate is displayed on an LCD in beats-per-minute in the following format:Rate = nnn bpm

WIRELESS MOBILE COMMUNICATION

The Cellular Concept

Introduction Frequency Reuse Channel Assignment Strategies Handoff Strategies Interference and System Capacity Improving Capacity In Cellular Systems

IntroductionEarly mobile radio systems

A single high powered transmitter (single cell) Large coverage area Low frequency resource utility Low user capacity

The cellular concept

A major breakthrough in solving the problem of spectral congestion and user capacity Many low power transmitters (small cells) Each cell covers only a small portion of the service area. Each base station is allocated a portion of the total number of channels Nearby base stations are assigned different groups of channels so that the interference between base stations is minimized

Frequency Reuse

l A service area is split into small geographic areas, called cells. Each cellular base station is allocated a group of radio channels. Base stations in adjacent cells are assigned different channel groups. By limiting the coverage area of a base station, the same group of channels may be reused by different cells far away. The design process of selecting and allocating channel groups for all of the cellular base stations within a system is called frequency reuse or frequency planning.

Frequency Reuse:

Cell Shapes

Geometric shapes covering an entire region without overlap and with equal area. By using the hexagon, the fewest number of cells can cover a geographic region, and the hexagon closely approximates a circular radiation pattern which would occur for an omni-directional antenna.

Frequency Reuse:

Excitation modes

Center-excited cell

Base station transmitter is in the center of the cell. Omni-directional antennas are used.

Edge-excited cell

Base station transmitters are on three of the six cell vertices.Sectored directional antennas are used.

Frequency Reuse:

The concept of Cluster

Consider a cellular system which has a total of S duplex channels available for use.The S channels are divided among N cells (cluster). Each cell is allocated a group of k channels.The total number of available radio channels can be expressed as S=kN.

Channel Assignment Strategies

Objectives:

Increasing capacity Minimizing interference

Classification:

Fixed channel assignment strategies Dynamic channel assignment strategies

Fixed channel assignment

Each cell is allocated a predetermined set of channels. Any call attempt within the cell can only be served by the unused channels in that particular cell. If all the channels in that cell are occupied, the call is blocked and the subscriber does not receive service.

Dynamic channel assignment

strategies

l Channels are not allocated to different cells permanently. Each time a call request is made, the serving base station requests a channel from the MSC.The switch then allocates a channel to the requested cell following an algorithm that takes into account: the likelihood of fixture blocking within the cell the frequency of use of the candidate channel the reuse distance of the channel other cost functions.

Handoff Strategies

Handoff:When a mobile moves into a different cell while a conversation is in progress, the MSC automatically transfers the call to a new channel belonging to the new base station. Processing handoffs is an important task in any cellular radio system.

Handoff Strategies:Requirements

Handoffs must be performed: Successfully;As infrequently as possible; Imperceptible to the users.

How to meet these requirements?

Specify an optimum signal level to initiate a handoff; Decide optimally when to handoff; Consider the statistics of dwell time.

Handoff Strategies:Signal strength measurementsl

First generation analog cellular systems:

Signal strength measurements are made by the base stations and supervised by the MSC.

Second generation systems:

Handoff decisions are mobile assisted;The MSC no longer constantly monitors signal strengths.

Interference and System

Capacity

Interference is the major limiting factor in the performance of cellular radio systems: a major bottleneck in increasing capacity often responsible for dropped calls

The two major types of system-generated cellular

interference are:

co-channel interference adjacent channel interference

Co-channel Interference andSystem Capacity

Co-channel InterferenceCells using the same set of frequencies are called cochannel cells, and the interference between signals from these cells is called co-channel interference. Unlike thermal noise which can be overcome by increasing the signal-to-noise ration (SNR), co-channel interference cannot be combated by simply increasing the carrier power of a transmitter. This is because an increase in carrier transmit power increases the interference to neighboring co-channel cells. To reduce co-channel interference, co-channel cells must be physically separated by a minimum distance to provide sufficientisolation due to propagation.

Co-channel Interference andSystem Capacity

The co-channel interference ratio is a function of the radius of the cell (B) and the distance between centers of the nearest cochannel cells (D). By increasing the ratio of D/R, the spatial separation between co-channel cells relative to the coverage distance of a cell is increased.Thus interference is reduced.

Adjacent Channel Interference

Interference resulting from signals which are adjacent in frequency to the desired signal is called adjacent channel interference.Adjacent channel interference results from imperfect receiver filters which allow nearby frequencies to leak into the passband.

Near-far effect:

If an adjacent channel user is transmitting in very close range to a subscriber's receiver, the problem can be particularly serious.

Adjacent Channel Interference

Adjacent channel interference can be minimized through careful filtering and channel assignments: By keeping the frequency separation between each channel in a given cell as large as possible, the adjacent channel interference may be reduced considerably.Channel allocation schemes can also prevent a secondary source of adjacent channel interference by avoiding the use of adjacent channels in neighboring cell sites. High Q cavity filters can be used in order to reject adjacent channel interference.

Power Control for Reducing Interference

In practical cellular radio and personal communication systems the power levels transmitted by every subscriber unit are under constant control by the serving base stations. This is done to ensure that each mobile transmits the smallest power necessary to maintain a good quality link on the reverse channel.Power control not only helps prolong battery life for the subscriber unit, but also dramatically improves the reverse channel S/I in the system. Power control is especially important for emerging CDMA spread spectrum systems that allow every user in every cell to share the same radio channel.

Improving Capacity In Cellular

Systems

As the demand for wireless service increases, the number of channels assigned to a cell eventually becomes insufficient to support the required numberof users.Techniques to expand the capacity of cellular systems :Cell splitting: increases the number of base stations in order to increase capacity.Sectoring: relies on base station antenna placements to improve capacity by reducing co-channel interference.Coverage zone: distributes the coverage of a cell and extends the cell boundary to hard-to-reach places.

Cell Splitting

Cell splitting is the process of subdividing a congested cell into smaller cells, each with its own base station and a corresponding reduction in antenna height and transmitter power. Cell splitting increases the capacity of a cellular system since it increases the number of times that channels are reused.

Cell Splitting

Sectoringl

The technique for decreasing co-channel interference and thus increasing systemcapacity by using directional antennas is called sectoring. The factor by which the co-channel interference is reduced depends on theamount of sectoring used.

Sectoring

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Documents

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