Basic Analog Electronics

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Basic Practical ElectronicsBasic Practical ElectronicsPassive components

Resistors, Capacitors, Inductors, Transformers, Diodes etc.

CircuitsCircuit analysis, voltage sources, current sources

Analog ElectronicsTransistors, Opamps, Simple analog Electronics circuits

Digital ElectronicsBasic Logic Gates and basic ICs, uPs, RAMs,

ROMs, ADCs, DACs, PALs etc.

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When selecting a resistor for a circuit, there are three parameters to consider

1. Resistance (Ω) 2. Power rating (W) 3. Tolerance (%)

4. Type???

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TYPES OF RESISTORS

Carbon Composition

Carbon mixed with a binder. Molded and baked. Ratio of carbon to binder determines resistance. Most common. Tolerances 10%.

CIRCUIT SYMBOLS

Carbon Film Better temp stability

Metal Film Better Tolerance 1%

Metal Oxide Better Temperature stability and

Tolerance (used in Most Logging

Equipment)

Wire wound

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WIRE WOUND: A conducting wire is wound on a ceramic form. Tend to be physically large. Low resistances. High power capability. Tolerances around 1%. Figure 1-8 shows some wire wound resistors.

EXAMPLE OF WIRE WOUND

RESISTOR Three terminal variable resistors

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COLOUR CODING OF RESISTORS

BBROYGBVGW

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CAPACITORSA capacitor is a device that stores energy as electrical

charge on it's plates.

The stored energy has to be a DC Voltage. This leads to capacitors acting like OPEN for DC while SHORT for AC

These plates are placed very close together with an Dielectric (insulator) in between.

Capacitance of a capacitor depends on the Area of two plates, how close they are and the dielectric type.

Capacitor parameters are 1. Capacitance value (uF –MicroFarads)2. Voltage Rating (V)3. Type

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Most commonly used capacitors

Made of electrolyte, Aluminum electrodes. Most common polarized capacitor (They have a +ve and –ve terminal)

•Applications: Ripple filters, timing circuits.

•Not very accurate, high values of capacitance, have leakage, drifting, not suitable for use in hf circuits.

•They WILL explode if the rated working voltage is exceeded or polarity is reversed, so be careful.

Electrolytic Capacitors

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Made of Tantalum Pentoxide. They are electrolytic capacitors but used with a material called tantalum for the electrodes. Superior to aluminum electrolytic capacitors, excellent temperature and better frequency characteristics.

Used in Logging Tools

More expensive than Aluminum but smaller size

Tantalums are also polarized so watch the '+' and '-' indicators.

Tantalum Capacitor

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Super Capacitors have very large capacitance value.

These are popular in DeskTop PCs and SMPS

Not used in Logging Tools

Super Capacitors

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Other types

Polyester Film

Tuning or 'air-core' capacitors.

Multilayer Ceramic

Metalized Polyester Film Adjustable Capacitors

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If a capacitor is marked like this 105, it just means 10+5zeros = 10 + 00000 = 1.000.000pF = 1000 nF = 1 µF

CAPACITOR CODING

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Capacitors in Parallel

C total = C1 + C2 + C3

Keep in mind that only the total capacitance changes, not the supplied voltage.

Capacitors in Series

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INDUCTORS

Inductor is essentially a device which stores energy in the form of magnetic field.

Common uses of Inductors are as Filter coils.

Most Important use is in Transformers, Relays

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TYPES OF INDUCTORS

BAR-COIL

SURFACE MOUNT

THIN FILMThe surface mount type inductors are very small in size and therefore deserve to be considered when spacebecomes and issue.

TOROIDAL

The surface mount type inductors are very small in size and therefore deserve to be considered when spacebecomes and issue.

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TransformerTransformer

Step down Step Up

Transformers work for AC

Only

Vp = Np = Is Vs Ns Ip

The core is usually made of Iron and is

laminated

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RELAYsRELAYs

Relays are electromagnetic switches which can be made to either SWITCH ON or OFF depending on the current in their coilA Relay has the following Pin connections below

NC – Normally Closed

NO – Normally Open

COM – Common

Coil -

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Some Typical Circuits - Voltage Divider

1) With two resistors in series, the sum of the voltage drop across each equals the total voltage drop across both.

2) To determine the voltage between the two resistors, we use the voltage divider formula

3) The voltage divider formula says Vout = Vin* (R2/R1+R2)

4) This turns out to be very useful

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Passive Components - Diodes

Schematic Symbols for DIODES

Diode is a electronic device that allows current to flow in one direction ONLY

There are many type of Diodes. Some basic types are1. Rectifier Diode2. Zener Diode3. Light emitting Diode

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DIODE, Transformer, Capacitor APPLICATIONS

Rectifiers

During the negative part of the cycle D1 does not conduct and no current flows to the load. In the full wave application it essentially is two half wave rectifiers combined and because the transformer secondary is centre tapped, D1 conducts on the positive half of the cycle while D2 conducts on the negative part of the cycle. Both add together.

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DIODE APPLICATIONS

Zener diodes work on the principle of essentially a constant voltage drop at a predetermined voltage

Voltage regulators

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OTHER DIODE APPLICATIONS

LEDs

LEDs usually have Gallium Arsenide Phosphide

Photodiodes

Opto-Coupler

Opto-Isolator

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1N34A Germanium Diodes

Germanium diodes have the advantage of an intrinsically low forward voltage drop, typically 0.3 volts; this low forward voltage drop results in a low power loss and more efficient diode, making it superior in many ways to the silicon diode. A silicon diode forward voltage drop, by comparison, is typically 0.7 volts. This lower voltage drop with germanium becomes important in very low signal environments (signal detection from audio to FM frequencies) and in low level logic circuits. As a result germanium diodes are

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Voltage and Current SourcesVoltage and Current Sources

An ideal voltage source is a voltage source that maintains the same voltage across the source's terminals no matter

what current is drawn from the terminals of the source or what current flows into

the terminals

Similarly an Ideal current source would

source the same amount of current no matter what voltage

develops

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Circuit Analysis 1Circuit Analysis 1

L R1 R2R

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R3

R4

V

In the Electrical circuit below what is the voltage across R3 and current in R4

C

12V

L= 2H, C= 1uF, R4=6 ohms, R2=4 ohms, R3=2 ohms, R1=3 ohms

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Circuit Analysis 2Circuit Analysis 2

Input is Sinewave Plot output

2.5V.

All three diodes are general purpose Silicon Diodes

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Circuit Analysis 3Circuit Analysis 3Two Electrical Bulbs each of 220V, 40W rating are connected in the manner shown

A. B.

220V Bulb1 Bulb2 220V Bulb1 Bulb2

Total light in Case A ________________ Total light in Case B (choices GT, EQ, LT)

Voltage Across Bulb1 Case A = _______ Volts, Current in Bulb2 Case B = _______

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TRANSISTORS

Transistors are semiconductor electronic devices that can amplify

currents or voltages when configured properly

There are many types of Transistors. For selecting a Transistor we need to know the application desired (type of Transistor, Voltage

(power rating) and max frequency of operation

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Most Transistors have three leads which must be connected the correct way round.

These days Transistors come in a variety of packages and sometimes can be difficult to recognize

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Besides Amplifying Transistors can also be connected as a Switch

TEST CIRCUIT for Transistor as a Switch

We use this type of configuration typically

inside our Logging Equipment to activate RELAYs by sending a remote control signal

to the base of the Transistor

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DARLINGTON PAIR:

Sometimes we need to amplify and handle large currents

1. Controlling Relays2. Driving Loudspeakers

In such cases we put a Small Signal Transistor TR1 (high gain but low current) in series with a Power Transistor TR2 (low gain but high current) as shown

The resulting composite Transistor is called a Darlington Pair. A Darlington Pair has High Gain as well as High Power

One can make the Darlington Pair by using two separate Transistors or buy

TRANSISTOR APPLICATIONS

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Simple Transistor Amplifier

Given below is a standard Common Emitter AC Amplifier. Transistor is Silicon NPN

Assume hfe () >> 100, Vbe = 0.7V

In

Out19.2 K 9.4K

10.8 K4.7 K

+15V AC Gain of the circuit = ________

DC Voltage at base of Transistor is _____

DC Voltage at Collector of Transistor is ______

DC Voltage at Emitter of Transistor is _______

DC Current from Collector to Emitter is ________

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One use of phase splitters is to provide input signals to a single-stage amplifier that uses two

transistors. These transistors are configured in such a way that the two outputs, 180º out of phase with

each other, combine. This allows more gain than one transistor could supply by itself. This "push-pull"

amplifier is used where high power output and good fidelity are needed:

PUSH-PULL AMPLIFIERS

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AMPLIFIER FREQUENCY RESPONSE

BANDWIDTH OF AN AMPLIFIERThe bandwidth represents the amount or "width" of frequencies, or the "band of

frequencies," thatthe amplifier is MOST effective in

amplifying.

B.W = f2-f1

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Analog Electronics – Operational Amplifiers

The input stage is a differential amplifier that works for AC also

High Input impedance

High Gain Voltage Amplifier. Typical > 100,000

Low Output Impedance to deliver several mA of current into load connected to the Output.

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Op Amps ApplicationsOp Amps ApplicationsCommon applications:• Inverting amplifier• Non inverting amplifier• Summing amplifier• Voltage follower• Instrumentation amplifiers• Filters

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Non-inverting AmplifierNon-inverting Amplifier

IN1

2o V

RR

1V

R1

R2

V IN

Vo

I=0

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Inverting AmplifierInverting Amplifier

V0+

R1 R2

VIN

Input Loop

Feedback Path

Output Loop

IN1

2o V

RR

V

I=0

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V1

V0+

V3

V2

RF

R1

R2

R3

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F2

2

F1

1

F0 V

RR V

RR V

RR

V

Summing Amplifier-MixerSumming Amplifier-Mixer

Also used in DACs – will see later

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Voltage followerVoltage follower

• Vout(ideal) = Vin

• High input resistance Rin

• Low output resistance

Used as a buffer

stage between any

two electronic

devices. Why?

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IInstrumentation nstrumentation AAmplifiermplifier

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Op Amp ChallengeOp Amp Challenge

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Filter TerminologyFilter Terminology

• Pass band is the range of frequencies over which it will pass an incoming signal

• Low pass filter pass low-frequency signal • High pass filter pass high frequency signals • Band pass filter passes a limited range of

frequencies• Band stop filters block signals occurring

between two given frequencies

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Filters

Background:

. An activeactive filterfilter is one that, along with R, L, and C components, also contains an energy source, such as that derived from an operational amplifier.

. A passive filterpassive filter is one that contains only R, L, and C components. It is not necessary that all three be present. L is often omitted (on purpose) from passive filter design because of the size and cost of inductors – and they also carry along an resistance(r) that must be included in the design.

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Passive FiltersPassive Filters

• Passive Components– Resistors– Capacitors– Inductors

• Use No Amplifying Elements– Transistors– Operational Amplifiers

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Passive FilterPassive Filter• No transistor, diodes, etc• Gain is always <= 1• Output load become part of circuit• Simplest electronic filters (consist of

resistors,inductors and capacitors)• Since resistance has the symbol R, inductance

the symbol L and capacitance symbol C, so filters exist in so-called RC, RL, LC and LCR varieties

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How Passive Filters WorkHow Passive Filters Work• Capacitors

– Block low frequency signals– Conduct high frequency signals

• Inductors– Block high frequency signals– Conduct low frequency signals

• Resistors– Have no frequency-selective properties

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Passive Analog Filters

Background: Four types of filters Four types of filters - “Ideal”- “Ideal”

lowpasslowpass highpasshighpass

bandpassbandpass bandstopbandstop

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Background: RealisticRealistic FiltersFilters::

lowpass highpasshighpass

bandpassbandpass bandstopbandstop


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Low Pass Filter Consider the circuit below.

R

CVI

VO

+

_

+

_

1( ) 1

1( ) 1OV jw jwC

V jw jwRCRijwC

Low pass filter circuit

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High Pass Filter Consider the circuit below.

C

RVi VO

+

_

+

_

( )1( ) 1

OV jw jwRCRV jw jwRCRi

jwC

High Pass Filter

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Active FilterActive Filter

• Combination of passive components and amplifiers

• High Q value • Able to achieve resonance frequency without

the use of inductors

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Low Pass Active Filter

R

C

-

+

Ra

Rf

X(s)Y(s)

RCs

RCR

RsH

a

f

1

1

1)(

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High Pass Active FilterHigh Pass Active Filter• Simplified Circuit

– Differentiator• Response

– At high frequencies the capacitor acts as a short. The gain becomes -R1/R2

– At low frequencies the capacitor is open and the signal is lost

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High Pass Active Filter

These are similar to active low pass filters, and may be constructed by cascading first- and second-order sections. Here’s a first-order section:

R

C-

+

Ra

Rf

X(s)Y(s)

RCs

s

R

RsH

a

f

11)(

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Required Filter OrderRequired Filter OrderTypically, we will have a requirement for a filter with a particular pass band, stop band, minimum/maximum pass band gain, and minimum stop band attenuation. The first thing we need to do is choose the filter type and order. We’ll assume the type has already been chosen, so we need to determine the order.

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V in

R 1

R 1

C 1

C 2

R 2

R 2

R fb

R i

V O

+

+

_

_

Band pass(100-200Hz) filter

fr2=200Hz fr1=100Hz

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V i n

R 1

R 1

C 1

C 2

R 2R i

R fb

V O

+

_

+

_

Band stop(100-200Hz) filterfr2=100Hz

fr2=200Hz

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ReviewReviewIn Logging we have to deal with Basic Electronics

Passive Electrical circuits consist of Resistors, Capacitors, Inductors, Transformers, Diodes

Active Electronics circuits consist of active devices like Transistors, Op-Amps plus passive components

Understanding of Basic Circuits like Amplifiers, Filters, Buffers, Mixers, Power supplies is important

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Basic Analog Electronics