electronic devices Lab MANUAL_

Electronic Devices Laboratory Department of ETCE .1

LIST OF EXPERIMENTS

I CYCLE

1. SYMBOLS , IDENTIFICATION AND CHECKING OF ELECTRONIC COMPONENTS

2. V- I CHARACTERISTICS OF SEMICONDUCTOR DIODE

3. V- I CHARACTERISTICS OF ZENER DIODE

4. V- I CHARACTERISTICS OF UJT

5. V- I CHARACTERISTICS OF JFET

6. INPUT & OUTPUT CHARACTERISTICS OF TRANSISTOR UNDER CB CONFIGURATION

7. INPUT & OUTPUT CHARACTERISTICS OF TRANSISTOR UNDER CE CONFIGURATION

Expt. No :1Date:

STUDY AND CHECKING OF ELECTRONIC COMPONENTS(Identification, color coding, Symbols, and checking of electronic components )

Manual prepared by Mr.N.Hariprasad ETCE DEPT. Sathyabama University Dr.Jeppiaar Nagar Chennai-119

Electron Devices Laboratory Department of ETCE 2

Aim: 1) To identify the given electronic components2) To under stand the colour coding scheme used in resistors and capacitors.3) To know about the symbols used to specify electronic components.4) To obtain the through knowledge about checking of the electronic components.

Identification of components

1) Diode: Diode is two terminal devices. Anode and Cathode are the two electrodes (denoted by A and K respectively) and the later is indicated by any distinct mark on the body of the component.

2) Transistor: BJT, FET, MOSFET all comes under the category of transistor. But in normal usage transistor straightaway means BJT. Some of the commonly used transistors’ package details are illustrated in the fig 1-2. (Using this we can identify the terminals only-not its type)

Sathyabama University Jeppiaar Nagar Chennai-119


Passive components: Resistors, Capacitors and inductors are the important passive components used in electronics. None of these elements (except electrolytic capacitor) has polarity. Some of the commonly used passive components are illustrated in fig 1-3

Colour code: If you are a bit serious about the electronics hobby I recommend learning the "Colour-Code". It makes life a lot easier. The same colour code is used for everything else, like coils, capacitors, rf-chokes, etc. Again, just the colour code associated with a number, like: black=0 brown=1 red=2, etc, etc. Refer fig 1-4



Example 1: For a Carbon 22000 Ohms or 22 Kilo-Ohms also known as 22K at 5% tolerance: Band 1 = Red, 1st digit Band 2 = Red, 2nd digitBand 3 = Orange, 3rd digit, multiply with zeros, in this case 3 zero's Band 4 = Gold, Tolerance, 5%

Example 2 : For a Precision Metal Film 19200 Ohms or 19.2 Kilo-Ohms also known as 19K2 at 1% tolerance: Band 1 = Brown, 1st digit

Band 2 = White, 2nd digit Band 3 = Red, 3rd digit Band 4 = Red, 4th digit, multiply with zeros, in this case 2 zero's Band 5 = Brown, Tolerance, 1% Band 6 = Blue, Temperature Coefficient, 6

Note : If the 3rd band is gold it means multiplying by 0.1. Example, 1.2 ohm @ 5% would be brown-red-gold-gold. 12multiplied by 0.1 gives 1.2 Don't get confused by gold as a resistance or a tolerance value. Just watch the location/position of the band.Do the exercises below.1st band, denominator: Brown (1) 2nd band, denominator: Black (0) 3rd band, how many zeros (1) 4th band, tolerance in %: gold (5) Answer: 1 0 1 = 100 ohm, 5% tolerance



1st band: _____ 2nd band: _____ 3rd band: _____ 4th band, tolerance in %: _____ Answer: ___________________

1st band: _____ 2nd band: _____ 0 3rd band: _____ 4th band, tolerance in %: _____ Answer: ___________________

1st band: _____ 2nd band: _____ 3rd band: _____ 4th band, tolerance in %: _____ Answer: ___________________

1st band: _____ 2nd band: _____ 3rd band: _____ 4th band, tolerance in %: _____Answer: ___________________

4700 ohm, 5% = yellow violet red, gold 100 ohm, 2% = brown black brown, red

1000 ohm, 5% = brown black red, gold 22 ohm, 1% = red red black, brown

150 ohm, 5% = ________________________ 270 ohm, 5% = _____________________

3300 ohm, 5% = ________________________ 10 ohm, 1% = ________________________

470 ohm, 2% = ________________________ 6800 ohm, 10% = ________________________

3K3, 5% = ________________________ 1K, 5% = ________________________

150 ohm, 1% = ________________________ 2M9, 10% = ________________________

10M, 10% = ________________________ 1 Mega Ohm, 5% = ________________________

1 ohm, 1% = ________________________ 3M9, 20% = ________________________

1200 ohm, 5% = ________________________ 1K2, 5% = ________________________

3900 ohm, 2% = ________________________ 100.000 ohm, 5% = ________________________

10K, 5% = ________________________ 10.000 ohm, 5% = ________________________

Symbols :



Checking of Components:



Diode : 1) Keep the Multimeter in resistance or continuity mode.2) Connect the two test probe on either side of the diode.3) Either it reads low resistance or shows high resistance.4) Reverse the probe connections5) Now the meter should read opposite to that of the step 3 i) If it is so then the diode is OK,

ii) In this case while showing the low resistance the electrode connected to the positive probe is anode.6) If the meter reads in the same way for both the connections then the diode is useless.

i) If it is low resistance, the diode is said to be shorted.ii) If it is high then the diode is open.

Transistor : 1) The transistor can be considered as two diodes ie The base emitter junction forms one diode and the

collector base junction forms the other.2) Individually check both the junctions and confirm both are OK.3) Also there must not be any collector emitter short.4) If we know the type and terminals of the transistor exactly then it can be straightaway inserted in the slot

provided in the digital multimeter (and the rotary switch of the meter pointing hfe) and read the value .If the hfe value is in between 50 and 300 the transistor is OK.

Passive components :1) For measuring resistors multimeters can be used.2) For measuring capacitors and inductors RLC meters, bridges are available.3) i) For Electrolytic capacitor connect the two probes of the multimeter to the either end of the device.

The meter immediately flases to low resistance and slowly returns to the high value. Remove one end of the probe for an instant and reconnect it .There must not be any change.

ii ) Reverse the connection and the meter re-shots. If it is so then the electrolytic capacitor is working.



Expt. No :2Date:

V - I CHARACTERISTICS OF PN JUNCTION DIODE

AIM: To plot the VI characteristics of a PN junction diode in both forward and reverse biased condition

To calculate its cut in voltage, forward resistance and reverse resistance. APPARATUS REQUIRED :

SLNO NAME OF THE APPARATUS RANGE TYPE QTY

1 Regulated power supply

0-30 V DC 1 No

2 Volt meter 0-30V MC 1 No

3 Ammeter (0-50mA), (0-50A)

MC Each 1 NO

4 Diode - 1N4001 1No

5 Breadboard - - 1 No

THEORY:

A diode is a PN junction formed by a layer of P-type and a layer of N-type semiconductor. When a PN junction is formed, the free electrons in the N-region diffuse across the junction and combine with holes in the P-region and so a depletion layer is developed. The depletion layer consists of ions which acts like a barrier for diffusion of charges beyond a certain limit. The difference of potential across the depletion layer is called the barrier potential. At 25 centigrade, this barrier potential is approximately equals 0.7 v for silicon diodes and 0.3V for germanium diodes. When the junction is forward biased the majority carriers acquired sufficient energy to overcome the barrier and the diode conducts. When the junction is reverse-biased the depletion layer widens and the barrier potential increases. Hence the majority carriers cannot cross the junction and the diode does not conduct. But there will be small leakage current due to minority carriers.

PROCEDURE:

FORWARD BIAS: The connections are made as shown in the circuit diagram. For forward bias the positive terminal of power

supply is connected to anode of the diode, negative terminal to cathode. The power supply is switched on. The forward voltage Vf across the diode is increased in small steps and the forward current is noted. The readings are tabulated.

A graph is drawn between Vf and If by taking Vf along x-axis.The inverse of the slope of the linear portion of the graph gives the forward resistance Rf of the diode Rf=Vf / If.

REVERSE BIAS:For reverse bias the positive terminal of the power supply connected to cathode of the diode and the negative

terminal to the anode of the diode. The power supply is switched on. The reverse bias voltage V r is increased in steps and reverse current Ir is noted in each step. The readings are tabulated. A graph is drawn between V r and Ir taking Vr

on x-axis. The reverse characteristics curve is approximately a straight line .

CIRCUIT DIAGRAM:



TABULATIONS:

FORWARD BIAS REVERSE BIAS

Vf (V) If(mA) Vr (V) Ir (A)

RESULT: The forward and reverse characteristics of the semiconductor diode has been plotted

The forward resistance of the diode = --------- The cut-in voltage of the diode = ---------

Expt. No :3Date:

V - I CHARACTERISTICS OF ZENER DIODE



AIM: To plot the VI characteristics of a ZENER diode in both forward and reverse biased condition

To calculate its cut-in voltage, forward-resistance and knee-voltage APPARATUS REQUIRED :


1 Regulated power supply

0-30 V DC 1 No

2 Volt meter 0-30V MC 1 No

3 Ammeter (0-50mA),

MC 1 NO

4 Zener Diode - FZ 5.1 V 1No


THEORYThe diodes which are designated to operate in the breakdown region are called Zener diodes. The other

names are avalanche diode or break down diodes. In avalanche breakdown, the conduction in reverse bias is due to avalanche multiplication of charge carriers .In Zener breakdown, the breakdown is due to direct rupture of covalent bonds because of the presence of strong electric field. Zener break down usually occurs in silicon PN-junction at reverse bias of less than 6v.Avalanche breakdown diodes will have higher breakdown voltages from several volts to several hundred volts.

CIRCUIT DIAGRAM

PROCEDURE: FORWARD BIAS: The connections are made as shown in the circuit diagram. For forward bias the positive terminal of power supply is connected to anode of the diode, negative terminal to cathode. The power supply is switched on. The forward voltage Vf across the diode is increased in small steps and the forward current is noted. The readings are



tabulated. A graph is drawn between Vf abd If by taking Vf along x-axis. The inverse of the slope of the linear portion of the graph gives the forward resistance R f of the diode R f = V f / If

REVERSE BIAS:The connections are made as per the circuit diagram. A multimeter with (0-250 A) & (0-10mA)

current range is used to measure the reverse current. First the (0-250A) range is connected in the circuit. The power supply is switched ON and the supply voltage is gradually increased. As the reverse bias voltage reaches the breakdown voltage, the current through the Zener diode increases rapidly, the breakdown voltage is noted. Before the breakdown the current is low. Hence to determine the current before breakdown the connection is changed such that the lower range of ammeter is connected in the circuit. The voltage is increased in small steps and the current in each step is noted. As the current reaches 0.2 milli-amperes the connection is changed to include (0-10mA) range and the expt is continued till a reverse current of 10mA.The 250mA is included and the expt is continued up to a current of 30mA..A graph is plotted between V r and I r

by taking V r in X-axis. The reverse conduction region is extended to meet the X-axis at a point, the value of the voltage at this point is the reverse breakdown voltage Vrb. The inverse of the slope of the reverse conduction region is the reverse resistance of the Zener, Rr= V r / Ir ohms.

TABULATIONS:

FORWARD BIAS REVERSE BIAS

Vf (V) If(mA) Vr (V) Ir (A)

ZENER DIODE: The forward resistance of the Zener diode =--------- The reverse resistance of the Zener diode = --------- The reverse breakdown voltage Vrb = ----------



Expt . No :4Date:

CHARACTERISTICS OF UJT AIM:

To determine the emitter characteristics of a UJT APPARATUS REQUIRED :


1 Regulated power supply 0-30 V DC 2 Nos 2 Uni Junction Transistor - 2N2646 1 No 3 Volt meter 0-30V MC 2 Nos4 Ammeter (0-30mA), MC 1 NO 5 Resistors 1K, 560ohms carbon Each 1No


THEORY:The UJT consists of a bar of lightly doped n-type silicon with a small piece of heavily doped P type material

joined to one side. The end terminal of the bar is designated as base B1 and base B2 and the P type region is taken as emitter E. Since the silicon region is lightly doped it has high resistance and can be represented as two resistors as shown in equivalent circuit .The P type emitter forms a P-N junction with N type silicon bar and thus junction is represented by a diode in the equivalent circuit. When a voltage is applied between two bases it divides between two resistances in the ratio of their values .Let V1 be the voltage across the resistor Rb1.Now when the emitter is forward biased and if the forward bias voltage is less than V1, the diode is actually reverse bias and the device will be in cutoff. If the emitter voltage is increased above V1 the emitter current flows, the voltage at which the device starts conduction is called peak voltage Vp, when the emitter voltage is increased beyond Vp the charge carriers are injected in to n-region and the resistance starts decreasing since the resistance depends on doping, now the device inters negative resistance region. In this region as voltage decreases the current reaches a certain limit the resistance is saturated, the voltage falls to a low value called valley voltage Vv, after this valley point if forward voltage is increased further the emitter current increases rapidly with slight increase in emitter voltage similar to forward biased diode.CIRCUIT DIAGRAM:



PROCEDURE:The connections are made as shown in the circuit diagram. First the lower range ammeter (0-25) mA

is connected in the circuit. The DRB is set to 100 K ohms. The power supplies are switched on. The voltage across base - 2 and base-1, Vb2 b1, is set to some desired value. The emitter voltage is increased. The emitter voltage is increased. At a certain voltage the device will just start conduction. The voltage just above this point is the peak voltage, Vp and it is noted. Then supply voltage is increased further. With increase in the supply voltage the emitter voltage falls and current increases. The readings are taken in this negative resistance region and tabulated. The emitter current cannot be increased beyond certain limit, even by increasing the power supply voltage. This happens because the resistance Rb1 in the conduction state is very much less than the series resistance 100K. Hence almost the full supply will be dropped across the series resistance. Now in order to increase the emitter current the series resistance is reduced in steps and the expt. is continued as before. When the emitter current reaches 0.25mA, the ammeter range changes to 0-10mA and the expt. is continued. The readings are tabulated.

The expt. is repeated with different constant voltages of Vb2 b1. A set of graph is drawn b/n emitter current and emitter voltage by taking emitter current along x-axis. The peak voltage and the valley voltages are marked on the graph.

TABULATION:

EMITTER CHARACTERISTICS OF UJT

RESULT: The emitter characteristics

of the given UJT are determined.

Intrinsic stand-off ratio =


Vb2 b1 = 15V Vb2 b1 = 5 V Vb2 b1 = 10 V

Ve (V)

Ie (mA) Ve (V) Ie (mA) Ve (V) Ie (mA)


Expt.No :5Date:

CHARACTERISTICS OF JFET

AIM: To determine the drain and transfer characteristics of JFET and hence to calculate the parameters of

JFET

APPARATUS REQUIRED :

SLNO

NAME OF THE APPARATUS RANGE TYPE QTY

1 Regulated power supply 0-30 V DC 2 Nos

2 Junction Field Effect Transistor - BFW 10 1 No

3 Volt meter 0-30V MC 2 Nos

4 Ammeter (0-30mA), MC

1 No

5 Resistors 1K, 560ohms carbon Each 1No


THEORY: The JFET or FET is a uni-polar transistor and its operation depends on only one type of charge either hole or electron. The FETS are voltage controlled devices. An n-channel FET consists of a bar of n-type silicon with two islands of p-type material embedded in the sides. The two terminals of the channels are called source and drain,. The free electrons enter the channel through source terminal and leaves though drain terminal. The two p-regions in the n-channel FET are internally connected and is called gate. Similarly in p-channel FET the two n regions are internally connected. In most of the JFET the drain and source terminals are interchangeable. The gate terminal of JFET is normally reverse biased and this mode of operation is depletion mode.

If the drain is forward biased with respect to source with gate shorted to source then the drain current increases as drain to source voltage increases. After a certain amount of voltage called pinch off voltage Vp the resistance of the channel increases high value and current attains saturation. This maximum value of drain current with gate shorted to source is called drain-source saturation current Idss.

The conduction through channel can be controlled by reverse biasing the gate. When gate is reverse biased an electric field develops in the gate channel junction which reduces the channel width and so the conduction through the channel is controlled, As the reverse bias gate voltage increases the drain current decreases. The gate source bias voltage required to reduce drain current to zero is designated as the gate cut-off voltage Vgs(OFF). Also Vgs (OFF) is equal to pinch off voltage Vp.

CIRCUIT DIAGRAM:



PROCEDURE:

DRAIN CHARACTERISTICS:The connections are made as shown in the circuit diagram. The drain

characteristics are plotted between drain source Vds and drain current Id with different constant gate to source voltage Vgs. First the gate terminal is shorted to source. The power supply in the drain circuit is switched ON. The drain to source voltage is varied in small steps and drain current is noted in each steps and the readings are tabulated. Then the short between the gate and source is removed and gate supply is switched ON. The expt. is repeated with different constant gate to source voltages. A set of graphs are plotted between Vds and Id by taking Vds on X-axis. The pinch off voltage and the drain source saturation current are marked in the graph. TRANSFER CHARACTERISTICS:

The same circuit is used to determine the transfer characteristics. The power supplies are switched ON. The gate to source voltage is varied in small steps and the drain current is noted in each steps and the readings are tabulated. The expt. is repeated with different constant drain to source voltage. A graph is plotted between Vgs and Id by taking Vgs on X-axis. The drain-source saturation current and pinch off voltage are marked on the graph.TABULATION:

DRAIN CHARACTERISTICS: TRANSFER CHARACTERISTICS: Vds = 15V

RESULT: The drain and transfer characteristics of the given JFET are determined and the parameters are calculated. The drain resistance , rd=

The transconductance , gm= The amplification factor , =


Vgs=0V Vgs=-1V Vgs=-5V

Vds(mA)

Id (mA) Vds (V) Id (mA) Vds

(V)

Id (mA)

Vgs (V) Id (mA)


Expt.No :6Date:

CHARACTERISTICS OF TRANSISTOR UNDERCOMMON BASE CONFIGURATION

Aim:

To determine the input & output characteristics of the transistor when operated on common emitter mode

APPARATUS REQUIRED :


1 Regulated power supply 0-30 V DC 2 NOs2 Transistor - BC 107 1 No

3 Volt meter (0-30V),(0-1V) MC Each 1No

4 Ammeter (0-30mA), MC 2 NOs5 Resistors 1K carbon 2Nos


Apparatus:1.DC power supply (0-30V) 2.MC ammeter (0-250A)& (0-30mA)3.FET voltmeter 4.Transistor BC1075.Resistors 100K,1K6.Breadboard

Theory: The transistor is a three terminal device. In a transistor one of the terminals can be made common to both input and output circuits. In common base mode the base is made common. In this mode the i/p is emitter and o/p is taken from collector. In CB mode Ie ,Veb & Ic, Vcb are input current and voltage, o/p current and voltage respectively. It is conventional to select i/p current & o/p voltage as independent variables.

Therefore the o/p current and i/p voltage can be expressed in terms of these independent variables.Veb = f1(Ie,Vcb)---1Ic = f2(Ie,Vcb)----2

The equation l represents the family of i/p characteristics .The i/p characteristics are plotted between Ie and Veb for different constant values Vcb .The equation 2 represents the family of o/p characteristics . The o/p characteristics are plotted between Ic & Vcb for different constant values of Ie.In a common emitter NPN transistor the current & voltages are all +Ve. But for PNP all the quantities are negative.

Procedure:The connections are shown in the circuit diagram. For i/p characteristics (0-30mA) range ammeter is

connected into o/p circuit . The i/p power supply is switched ON. The i/p voltage Veb is varied in small steps and i/p current Ie is noted by keeping the o/p voltage Vcb as zero.



The o/p circuit power supply is switched on and Vcb is set to 1V and the expt is repeated as before by maintaining Vcb at 1V.Again the expt can be repeated for different constant values of V cb .The readings are tabulated. A graph is drawn b/w Ie & Veb.

Output Characteristics:The i/p current is set to a constant value say 50A. The o/p voltage Vcb is varied in small steps and

the o/p current Ic is noted .The expt is repeated for different constant values of emitter current. A graph is drawn.

CIRCUIT DIAGRAM:

Tabulations:Input Characteristics:

Vcb = 0V Vcb = 1V Vcb = 5V

Veb (V)

Ie (A) Veb (V) Ie (A) Veb (V) Ie (A)

Output Characteristics:

Ie = 50A Ie = 75A Ie = 100A

Veb (V)

Ie (A) Veb (V) Ie (A) Veb (V) Ie (A)

Result: The i/p and o/p characteristics are drawn and h-parameters are calculated.

Expt .No:6Date:

CHARACTERISTICS OF TRANSISTOR UNDERCOMMON EMITTER CONFIGURATION

AIM:To determine the input & output characteristics of the transistor when operated on common emitter mode .



APPARATUS:1.DC power supply (0-30V) 2.MC ammeter (0-250A)& (0-30mA)3.FET voltmeter 4.Transistor BC1075.Resistors 100K,1K6.Breadboard

THEORY: The transistor is a three terminal device. In a transistor one of the terminals can be made common to both input and output circuits. In common emitter mode the emitter is made common. In this mode the i/p is given to the base and o/p is taken from collector. In CE mode Ib ,Vbe Ic & Vce are input current and voltage, o/p current and voltage respectively. It is conventional to select i/p current & o/p voltage as independent variables.

Therefore the o/p current and i/p voltage can be expressed in terms of these independent variables.Vbe = f1(Ib,Vce)---1Ic = f2(Ib,Vce)----2

The equation l represents the family of i/p characteristics .The i/p characteristics are plotted between Ib and Vbe for different constant values Vce .The equation 2 represents the family of o/p characteristics . The o/p characteristics are plotted between Ic & Vce for different constant values of Ib.In a common emitter NPN transistor the current & voltages are all +Ve.But for PNP all the quantities are negative.

PROCEDURE:The connections are shown in the circuit diagram. For i/p characteristics (0-30mA) range ammeter is

connected into o/p circuit . The i/p power supply is switched ON. The i/p voltage Vbe is varied in small steps and i/p current Ib is noted by keeping the o/p voltage Vce as zero. The o/p circuit power supply is switched on and Vce is set to 1V and the expt is repeated as before by maintaining Vce at 1V.Again the expt can be repeated for different constant values of V ce .The readings are tabulated. A graph is drawn b/w Ib & Vbe.

OUTPUT CHARACTERISTICS:The i/p current is set to a constant value say 50A. The o/p voltage Vce is varied in small steps and

the o/p current Ic is noted .The expt is repeated for different constant values of base current. A graph is drawn.

CIRCUIT DIAGRAM:



TABULATION:INPUT CHARACTERISTICS:

Vce = 0V Vce=1V Vce=5V

Vbe (V)

Ib (A) Vbe (V) Ib (A) Vbe (V) Ib (A)

OUTPUT CHARACTERISTICS:

Ib = 50A Ib = 75A Ib = 100A

Vce (V)

Ic (mA) Vce (V) Ic (mA) Vce (V) Ic (mA)

RESULT: The i/p and o/p characteristics are drawn and h-parameters are calculated.


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