EDC LAB Manual

M.S.P.VELAYUTHA NADAR M.S.P.VELAYUTHA NADAR M.S.P.VELAYUTHA NADAR M.S.P.VELAYUTHA NADAR

LAKSHMITHAIAMMAL LAKSHMITHAIAMMAL LAKSHMITHAIAMMAL LAKSHMITHAIAMMAL

POLYTECHNIC COLLEGEPOLYTECHNIC COLLEGEPOLYTECHNIC COLLEGEPOLYTECHNIC COLLEGE

SIVAGAMIPURAM, PAVOORCHATRAM-627808

THIRUNELVELI DISTRICT, TAMILNADU

[email protected]

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

ELECTRONIC DEVICES ELECTRONIC DEVICES ELECTRONIC DEVICES ELECTRONIC DEVICES AND CIRCUITS LABAND CIRCUITS LABAND CIRCUITS LABAND CIRCUITS LAB

YEAR: II SEMESTER: III

AUTHOR:

MS. N.Kowsalya Devi,B.E., Lecturer/ECE

PUBLISHER: M.S.P.V.L. POLYTECHNIC COLLEGE

PAVOORCHATRAM – 627 808

Department of Department of Department of Department of ECEECEECEECE EDC Lab ManualEDC Lab ManualEDC Lab ManualEDC Lab Manual

1

CONTENTS

S. No. Experiment Name Page No.

1. V-I Characteristics of PN Junction Diode 3

2. V-I Characteristics of Zener Diode 9

3. HW, FW with and without filter 17

4. Bridge Rectifier with & Without filter 25

5. VI Characteristics of Regulator 33

6. Input Output Characteristics of Common Emitter Transistor 39

7. Frequency Response of RC Coupled Amplifier 45

8. Emitter Follower 51

9. Negative Feedback Amplifier 55

10. RC Phase Shift Oscillator 61

11. Hartely & Colpitts Oscillator 67

12. Characteristics of JFET 75

13. Common Source Amplifier 81

14. Characteristics of UJT 87

15. UJT Relaxation Oscillator 93

16. Characteristics of SCR 99

17. Diac & Triac Characteristics 105

18. Clipper, Clamper & Voltage Doubler 113

19. LDR Photo Diode & Photo Transistor Characteristics 125

20. Solar Cell and Opto Coupler 131

21. Extra Syllabus: Astable Multivibrator 137


2

G

+ -

+

-

470Ω

RPS (0-30) V (0-1) V IN24001

(0-50) mA

K

A

A

V

Characteristics of PN Junction Diode

Forward Bias:

Reverse Bias:

+


3

1. V-I CHARACTERISTICS OF PN JUNCTION DIODE Aim:

To draw the voltage – current characteristics of PN junction diode under

forward and reverse bias condition and determine cut in voltage, reverse

saturation current and forward dynamic resistance.

Apparatus Required:

Theory:

A PN junction is formed by diffusing P-type material to one half side and

N-type material other half side. The plane dividing the two zones is known as

a junction.

Forward Bias:

When the positive terminal of the external battery is connected to the P-

region and negative terminal is connected to the N-region. Then it is called

as forward biased PN junction.

S. No Name of the Apparatus Range Quantity

1. PN Junction Diode IN4001 1 2. RPS (0-30)v 1 3. Resistor 470Ω 1 4. Voltmeter (0-1)v 1 5. Voltmeter (0-15)v 1 6. Ammeter (0-50)mA 1 7. Ammeter (0-50) µ A 1 8. Bread board -- 1 9. Connecting wires -- 1set

-


4

Model Graph:

Tabulation:

Forward Bias:

S. No Voltage In Volts(V F) Current In mA (I F)

If (m

A)

Vf (Volts) Vr (Volts)

Ir (

mA

)


5

Reverse Bias:

When the negative terminal of the external battery is connected to the

P-region and positive terminal is connected to the N-region. Then it is called

as reverse biased PN junction.

Procedure:

• The connections are made as shown in the circuit diagram.

• The power supply is switched ON

• The voltage in the RPS is varied and the corresponding Ammeter &

Voltmeter readings are noted and tabulated.

Graph:

The graph is drawn by taking voltage along x-axis and current along y-axis.


6

Tabulation:

Reverse Bias:

S. No Voltage In Volts (V R) Current In µA (IR)


7

Precaution:

Before connect the diode in the circuit check the resistance in

forward and reverse bias condition.

Voltmeter should be connected in parallel at any time.

Ammeter should be connected in series at any time. Result:

Thus the V-I characteristics of PN Junction diode under forward and

reverse bias condition was drawn and determined the cut in voltage, reverse

saturation current and forward dynamic resistance

Cut in voltage -----------------------------------------

Forward dynamic resistance ----------------------

Reverse saturation current ------------------------

Reverse Dynamic resistance -----------------------

Application:

• It is used in clipper and clamper circuits.

• As a switch in logic circuits used in computers. Viva Questions:

1. What is meant by energy gap?

2. Define valence band and conduction band?

3. What is the major difference between switching diode and a rectifier

diode?

4. What is dynamic resistance?

5. What is meant by p- type and n-type semiconductor?


8

Characteristics of Zener Diode:

Circuit Diagram:

Forward Bias:


9

2. V-I CHARACTERISTICS OF ZENER DIODE

Aim:

To draw the V-I characteristics of Zener diode under forward and

reverse bias condition and determine cut in voltage, reverse saturation current

and forward and reverse dynamic resistance.

Apparatus Required:

Theory:

A Zener diode is designed to operate in the reverse breakdown region.

It is heavily doped to reduce the reverse breakdown voltage. This causes a

very thin depletion layer. As a result, a Zener diode has a sharp breakdown

voltage.

Forward bias:

When the positive terminal of the external battery is connected to the

anode and negative terminal is connected to the cathode. When the applied

voltage is zero, no current flows through the Zener diode. When the forward

voltage is increased, the barrier is reduced and the current starts flowing in the

circuit.

S. No. Name of the Apparatus Range Quantity 1. Zener diode FZ 5.1 1 2. RPS (0-30)v 1 3. Resistor 470Ω 1 4. Voltmeter (0-1)v 1 5. Voltmeter (0-15)v 1 6. Ammeter (0-50) mA 1 7. Bread board -- 1 8. Connecting wires -- 1set


10

Reverse Bias:


11

Reverse Bias:

When the negative terminal of the external battery is connected to the

anode and positive terminal is connected to the cathode. Following actions

are takes place in the reverse bias condition. The diode current increases

rapidly. The reverse voltage VZ across the diode remains almost constants.

Procedure:


• The power supply is switched ON

• The voltage across the diode is varied by varying the RPS

• The corresponding voltmeter and ammeter readings are noted and tabulated for both forward and reverse bias.


12

Model Graph:

Tabulation:

Forward Bias:

S. No Forward Voltage in volts (V) Forward Current in (mA)

Ir (

Ma)

Vf (Volts) Vr (Volts)

If (m

A)


13

Graph:

Forward Bias:

The graph is drawn by taking forward voltage along x-axis and forward

current along y-axis.

Reverse Bias:

The graph is drawn by taking Reverse voltage along x-axis and Reverse

current along y-axis.

Precaution:

First identify the terminals that means, namely anode and cathode then connect the diode in the circuit.

Result:

Thus the characteristics of Zener diode under forward and reverse bias

condition was obtained.

Cut in voltage = ----------------

Break down voltage = ----------------

Forward dynamic resistance = ---------------

Reverse dynamic resistance = ----------------


14

Tabulation:

Reverse Bias:

S. No Reverse Voltage in Volts (V) Reverse Current in (mA)


15

Application:

• As a voltage regulator

• As a fixed voltage reference in transistor biasing circuits

• As peak clippers or limiters in wave shaping circuits

• For meter protection against damage from accidental application

Viva Questions:

What is Zener breakdown?

What is avalanche breakdown?

What is the difference between the ordinary PN diode and Zener

diode?

What is meant by doping?

Why it is called Zener diode?


16

Half Wave Rectifier (Without Filter Circuit)

Half Wave Rectifier (With Filter Circuit)


17

3. OBSERVE THE WAVEFORMS OF HALF WAVE & FULL WAVE RECTIFIER

Aim:

To construct half wave & full wave rectifier circuits using diodes & observe the input & output wave forms with & without filter. Apparatus Required:

Apparatus Range Type Quantity CRO - - 1

Multi meter - Digital 1 Transformer 9V-0-9V Core 1

Diode IN4001 2 Capacitor 1000 µf - 1 Resistor 2kΩ - 1

Precautions:

• It should not be exposed long in moisture & high temperature. • It should not be overloaded. • Handle all the control carefully. • Don’t make short circuit connection. • Safety depends upon good earthen; always keep earth connections in

good condition. • In case of fire do nut throw water on a live wire & equipment, it is

dangerous. The best remedy is to disconnect the main supply immediately.

• The electric fire should be extinguish with liquid carbon dioxide type extinguish or dry sand.

• Don’t touch the live terminal. • The instruments should be kept in a clean & dry room & must not be

operated in explosive, corrosive, dustily or moist environments. • The ventilation holes must not be covered. • If condensed water exists in the instrument, it should be acclimatized

before switching on. • Select proper type (i.e. A.C (or) D.C.) & Range of meters. • Switch on/switch OFF time inverse/reduce supply gradually not

suddenly. • You should check the transformer before connection. • Don’t make any short circuit while working. • Never temper with CRO • CRO should not be exposed long in moisture & high temperature. • CRO should not be overloaded. • CRO should not be over Bright. • Handle all the controls carefully.


18

CRO 230 V AC Supply

2K

9V

A K

K A

9V

Full Wave Rectifier (Without Filter Circuit)

Full Wave Rectifier (With Filter Circuit)


19

Procedure:

Without Filter:

• Test your transformer: Give 230V, 50Hz source to the primary coil of the transformer & observe the AC wave forms of rated value without any distortion at the secondary of the transformer.

• Connect you circuit to the secondary terminals of the transformer. • Connect your CRO across the load. • Keep the CRO switch in ground mode & observe the horizontal

line & adjust it to the x axis. • Observe the waveform by using CRO & draw the waveforms.

With Filter:

• Connections are made as per the circuit diagram. • Connect the capacitor across the load resistance & proceed with

the above procedure.

Theory:

Half Wave Rectifier:

Half Wave Rectifier is an electronic circuit which converts AC voltage

into a pulsating DC voltage in one half cycle of the voltage AC voltage.

Full wave rectifier:

Full wave rectifier is an electronic circuit which converts AC voltage into

a pulsating DC voltage in both half cycles of the applied AC voltage.


20

Half wave Rectifier Tabulation:

Description Amplitude (V) Time Period

Input voltage waveform

Output voltage waveform without filter

Output voltage waveform with filter


21

Graph:

Graph is drawn between time in x axis & amplitude in y axis.

Result:

Thus the half wave & full wave rectifier was constructed & observed the input & output wave forms with & without filters.

Application:

• Radio, TV

• Computer

Employment:

• Battery charger, emergency light, Eliminator manufacturing.

• All type of electronic industry using these circuits.


22

Full wave Rectifier Circuit Tabulation:

Description Amplitude (V) Time Period

Input voltage waveform

Output voltage waveform without filter

Output voltage waveform with filter


23

Viva Questions:

1. What is rectifier?

2. Which rectifier is mostly used? Why?

3. Which components are used for rectification?

4. What is filter?

5. What are the types of filter?

6. Why the filter used in rectifier circuit?

7. What are the types of rectifier depends upon single phase

supply?

8. What is RMS value?

9. What is DC value?

10. Define transformer utility factor?

11. What is rectifier efficiency?

12. What is the function of transformer?

13. Why step down transformer used for rectification?

14. What is ripple factor?

15. What is peak inverse voltage?

16. How many no. of diodes are used in full wave rectifier?

17. Which rectifier circuit has low efficiency? Why?

18. How much efficiency in the full wave, half wave rectifier?

19. What are the types of phase rectifier?

20. What are advantages of three phase rectifier compound to the

single phase?


24


25

4. BRIDGE RECTIFIER

Aim:

To construct and determine the regulation characteristics of Bridge Rectifier using with and without filter. Apparatus Required:

S. No. Apparatus Required Range Quantity

1. Transformer 9– 0– 9 V 1

2. Diode IN4001 4

3. Capacitor 1000µF 1

4. Bread Board -- 1

5. Connecting Wires -- 15

6. CRO (0-20)MHz 1

7. Resistor 2K 1

Theory:

Bridge rectifier is a full wave rectifier. It consists of four diodes arranged in the form of a bridge. It utilizes the advantages of the full wave rectifier and at the same time it eliminates the need for a centre tapped transformer. The supply input and the rectified output are the two diagonally opposite terminals of the bridge.


26


27

Procedure:

Without filter:

Test your transformer. Give 230v,50Hz source to the primary coil of

the transformer & observe the A.C voltage waveforms of rated

value without any distortion at the secondary of the transformer .

Connect your CRO across the load.

Keep the CRO switch in ground mode and observe the horizontal

line & adjust it to the Xaxis.

Switch the CRO into DC mode & observe the waveform.Note its

amplitude Vm and frequency from the screen along with its

multiplication factor.

Switch on the CRO into AC mode and observe the waveform. Note

its amplitude Vm and frequency from the screen along with its

multiplication factor.

With filter:

Rig up the circuit as per the circuit diagram.

Connect the capacitor across the load resistance & proceed with the

above.

`


28

ModelGraph:

Tabular Column:

S. No Description Amplitude (v) Time Period (ms)


29

Advantages:

DC saturation effect does not occur.

The transformer which is connected to bridge rectifier can be small in size for a given output and the current flows in both primary and secondary during both positive and negative cycle of the AC supply.

Transformer with centre tap in secondary is not required.

As two diodes are connected in series, in each conducting path of positive and negative cycle the peak inverse voltage is shared by both the diodes equally, hence it is suitable for high voltage application.

Disadvantages:

Additional two diodes are required.

Common point for earthen the source and the load is not available.

The rectifier efficiency is slightly less than the full wave rectifier circuit

as the voltage drop and losses are higher as the two diodes are

connected in series.

Application:-

It is used in Radio circuits

It is used in electronic power supply

It is used in communication system


30


31

Viva Questions:

What is the use of filter?

What are the different types of filters?

What is the different between Full Wave Rectifier and bridge rectifier?

What is meant by TUF?

Result: Thus the Bridge Rectifier using with and without filter was constructed and output waveforms were drawn.


32


33

5. V-I CHARACTERISTICS OF VOLTAGE REGULATOR

Aim: To construct and determine the characteristics of Voltage Regulator. Apparatus Required:

S. No. Apparatus R equired Range Quantity

1. RPS (0-30)V 1

2. Zener Diode FZ 5.1 1

3. Resistor 470Ω 1

4. Voltmeter (0 –15) V 1

5. Ammeter (0 – 50) mA 1

6. DRB -- 1

7. Bread Board -- 1

8. Connecting Wires -- 1set

Theory:

A voltage regulator (Regulated power supply) may be defined as an electronic circuit, which maintains an almost constant voltage across its output terminals irrespective of variations in the load current or in the supply voltage. A zener diode can readily be used as voltage regulator element to maintain constant voltage at the output. When a zener diode operates in zener breakdown region (under reverse bias condition), the voltage across it is constant for a large change in current through it. Therefore as long as the input voltage is greater than the zener voltage, it operates in breakdown region and maintains constant voltage across the load resistor even there is a change in input voltage or in load current. A series feedback voltage regulator employs feedback to hold the voltage almost constant despite changes in line voltage and load current.


34

Tabulation: Regulation for Input Voltage Variation: Rl = 1 k Ω

Vi (v) It (mA) IL(mA) V o(v)

Tabulation: Regulation for Load Current Variation: Vi = 10v

Rl (K Ω ) IL (mA) IL(mA) V o(v)


35

Procedure: Regulation for Input Voltage Variation:

Connections are made as shown in circuit diagram.

Here resistance of the load is constant.Input supply voltage is varied and

corresponding total current, load current, ammeter readings & output

voltage, voltmeter readings are noted and tabulated.

Regulation for Load Variation: Connections are made as shown in circuit diagram.

In this fixed supply voltage is given and load resistance is varied and

corresponding total current , ammeter readings are noted and tabulated.

Advantages:

High efficiency

Power loss is less.

Disadvantages:

Complex circuit and cost is high

Additional circuits are needed to protect against over load and short circuit.

Graph: Regulation for Input Voltage Variation: Graph is drawn by taking VL in x axis and IL in y axis. Regulation for Load Current Variation: Graph is drawn by taking IL in x axis and V0 in y axis.


36

Series Voltage Regulator

Vo (V)

Vin(V)

Vo (V)

Rv (KΩ)


37

Applications:

It can be used for variable load application

It is suitable for high voltage and low current circuits

Viva questions:

What is the need for voltage regulator?

Where it is used?

Mention the types of voltage regulators?

What is the difference between zener diode and series voltage regulator?

Result:

Thus the characteristics of Series Voltage Regulator were constructed and

determined the regulation.

Regulation of Series Voltage Regulator is ____________ %.


38

A

V

A

V

-

+

-

+

-

RPS (0-30) V

(0-1) V +

RPS (0-30) V

(0-10) mA 1.2 KΩ

+

(0-15) V

(0-100) µA - 470 KΩ

BC 147

IC

VCE

C

+

- E

B

VBE

IB

+

-

Characteristics of CE Configuration:

Pin Details:

BC 147

E B C


39

6. INPUT OUTPUT CHARACTERISTICS OF COMMON EMITTER TRANSISTOR

Aim: To draw the input and output characteristics of common emitter configuration, find input and output resistance. Apparatus Required:

S. No Apparatus Range Quantity 1. Transistor BC147 1 2. Resistor 470Ω 1 3. Resistor 1.2kΩ 1 4. RPS (0-30)v 1 5. voltmeter (0-1)v 1 6. voltmeter (0-30)v 1 7. Ammeter (0-100)mA 1 8. Ammeter (0-50)µA 1 9. Ammeter (0-100)µA 1 10. Bread board - 1 11. Connecting wires - 1set

Theory:

In this circuit arrangement input is applied between base and emitter

and output is taken from the collector and emitter. Here emitter of the

transistor is common to both input and output.

Input Characteristics:

It is the curve between base current IB and base emitter voltage VBE at

constant collector emitter voltage.

Input Resistance:

It is defined as the ratio of change in base-emitter voltage to the change

in base current at constant VCE. B

BEI

∆I∆V

R =


40


Model Graph: Output Characteristics:

I b(µ

A)

Vec

= 1

0V

Vec

= 5

V

Vec

= 0

V

Vbe (Volts)

I C(m

A) Ib = 80µA

Ib = 60µA

Ib = 40µA

Vce = (Volts)


41

Output Characteristics:

It is the curve between collector current IC and collector-emitter voltage at constant base current IB. Output Resistance:

It is defined as the ratio of change in collector-emitter voltage to the

change in collector current at constant IB. C

CEO

∆I∆V

R =

Procedure:


The connections are made as per in the circuit diagram

By using RPS VCE is kept at a constant voltage.

Base-emitter voltage (VBE) is increased in number of steps and the corresponding values of base current IB are noted and tabulated.


The connections are made as per in the circuit diagram

By using RPS IB is kept at a constant current.

Collector-emitter voltage VCE is increased in number of steps and the corresponding values of collector current IC are noted and tabulated.


42

Tabulation:


S. No VCE=0V VCE=5V VCE =10V

VBE(V) IB(µA) VBE(V) IB(µA) VBE(V) IB(µA)

Tabulation:


S. No IB=40µA IB=60µA IB=80µA

VCE (V) IC (mA) VCE (V) IC (mA) VCE (V) IC (mA)


43

Graph:


Base current (IB) is taken along y-axis, base-emitter voltage (VBE) is

taken along x-axis.


Collector current (IC) is taken along the y-axis, collector-emitter voltage

(VCE) is taken along x-axis.

Result:

Thus the input and output characteristics of common emitter

configuration was drawn and the

Input resistance = -------------------

Output resistance = ----------------- Application:

• It is used as a amplifier in audio frequency application.

• It is used in digital computers

• It is used in satellites

• It is used in mobile phones

• It acts as a switch. Viva Questions:

1. What is meant by transistor?

2. Which configuration is commonly used?

3. Draw the symbol of NPN, PNP transistor?

4. What is meant by transistor biasing?

5. Which configuration has 180° phase shift differe nce?


44

RC Coupled Amplifier:


45

7. RC COUPLED AMPLIFIER

Aim:

To construct a RC coupled amplifier & plot the frequency response characteristics & determine the lower, upper cut-off frequency & bandwidth. Apparatus Required:

S. No. Apparatus Range Quantity 1 Power Supply (0-30) V 1 2 CRO (0-20) MHz 1 3 Function Generator (0-1) MHz 1 4 Capacitor 100 µF 1 5 Capacitor 5µF 1 6 Resistors 2.5KΩ 1 7 Resistors 27.5KΩ 1 8 Resistors 10KΩ 1 9 Resistors 100KΩ 1

10 Resistors 1KΩ 1 11 Semi Conductors BC 547 1 12 Semi Conductors BC 107 1

Precautions:

1. Never temper with CRO. 2. Oscilloscope should not be exposed long in moisture & high

temperature. 3. Oscilloscope should not be overloaded. 4. Oscilloscope should not be over bright. 5. Handle all the controls carefully. 6. It should be noted that generators always deliver an output but

never take input & hence care should be taken that no input is given in any form to the output ports.

7. The ventilation holes must not be covered. 8. If condensed water exists in the instruments it should be

acclimatized before switching on. 9. The instruments should be kept in a clean & dry room as must not

be operated in explosive, corrosive, dusty. 10. The display can only be cleaned with water or washing benzene

(not with spirit).


46

Model Graph:

3 dB

F1 Low F2 High FREQUENCY (HZ)

GA

IN (

DB

)


47

All the measuring terminals are to be connected to the protective earth contact

of the inlet.

1. The mains plug shall only be inserted in a socket outlet connected with protective earth contact.

2. The protective action must not be negated by the use of an extension cord without a protective conductor.

3. Any interruptions of the protection conductors inside or outside the instruments or disconnections of the protective earth terminals are likely to make the instruments dangerous. The main plug should be inserted before connections are mode to test circuits.

4. All the connections should be tight. 5. Power supply should not be overloaded. 6. Don’t vary the supply suddenly.

Procedure:

1. Connect the circuit as per the circuit diagram. 2. Set Vs = 50 mV (say). Using the signal generator. 3. Keeping the input voltage constant, vary the frequency 0Hz to 1MHz

in regular steps & note down the corresponding output voltage. 4. Plot the graph: gain (dB) Vs frequency. 5. Calculate the bandwidth from graph. 6. Find the upper & lower cut-off frequency.

Result:

Lower cut-off frequency = Upper cut-off frequency = Bandwidth = Thus the RC coupled amplifier was constructed & its frequency response characteristics was plotted & its upper & lower cut-off frequency & bandwidth was determined. Application:

The RC coupled amplifiers have excellent audio fidelity over a wide range of frequency. Therefore, they are widely used as voltage amplifiers e.g in the initial stages of public address system. The gain is constant, over the audio frequency range which is the of most importance region for speech, music etc.


48

Tabulation:

Frequency (Hz) Voltage (V) Gain Vo/Vi Gain db 20 log

Vo/Vi


49

Employment:

• This amplifier used in speech and music system • All kind of electronics industry used

Viva Questions:

1. What is amplifier?

2. What are the classifications of amplifier?

3. What is the range of frequency value in audio amplifier?

4. What is coupling?

5. What are the types of coupled amplifier?

6. Define stability factor?

7. What are the different methods for transistor biasing?

8. Which types of bias is mostly used?

9. Which type of bias is used for RC coupled amplifier circuits?

10. What is cascaded amplifier?

11. Define gain.

12. What is the unit gain? Why?

13. Define frequency?

14. What is frequency response?

15. What are the three regions in frequency response characteristics?

16. Define bandwidth?

17. What is meant by operating point?

18. What is the reason for fall in gain at lower & upper out-off frequency

region?

19. Which types of amplifier are used in oscilloscope?

20. Which types of amplifier are used in electronic power supplies?

21. What is common mode rejection ratio?

22. What is a driver circuit?

23. Why is negative feedback used in RC coupled amplifier?

24. What is power amplifier?


50

Emitter Follower:


51

8. EMITTER FOLLOWER

Aim:

To construct a emitter follower circuit & find its frequency response. Theory:

Emitter follower is also known as common collector amplifier. In this amplifier, collector base junction act as input & emitter base junction act as output. Thus the output taken across the emitter exactly follows their input voltage variation. Hence it is named as emitter follower. Bias voltage VB is received from VCC by means of potential divider R1 & R2. So the circuit exploited emitter in series with the transistor collector terminal and no emitter by pass capacitor is employed. The capacitors CC1, CC2 circuit as coupling capacitor. Procedure:

1. Connections are made as per the circuit diagram. 2. The i/p S/L is given & the value is noted. 3. The frequency of i/p S/L is varied & the corresponding o/p voltage is

noted. 4. Then the voltage gain in dB is calculated using the formula gain in

db = 20 logi

O

VV

.

5. The graph for the frequency Response of CC amplifier is drawn using the above values.


52

Tabulation:

Sl. No. Frequency in Hz Output Voltage V O

(volts) Gain in dB = 20 log

(VO/Vi)


53

Application:

1. The voltage gain of emitter follower as unity, thus it is used as buffer

amplifier.

2. It is used as impedance matching network.

Result:

Thus the Emitter Follower is constructed & the frequency Response is formed.

Viva Question:

1. Other name of Emitter follower? 2. Why it is called emitter follower? 3. Advantages of emitter follower?


54


55

9. COMMON EMITTER AMPLIFIER Aim:

To construct Common Emitter Amplifier and draw its frequency response curve. Apparatus Required:


1. Transistor BC147 1

2. Capacitor 3.3µF 470µF

2 1

3. Resistor 1.2 KΩ 2KΩ

2 2

4. FGR -- 1

5. Power supply (0 – 30) V 1

6. CRO -- 1

7. Bread Board -- 1


Theory:

When an AC signal is applied to the base it makes the base positive in the first half cycle and negative in the second half cycle. Therefore the base and collector currents will increase in the first half cycle. When base emitter junction is more forward biased. However, they will decrease in the second half cycle when the base emitter junction is less forward biased. The circuit uses by pass capacitor C to eliminate AC degeneration ie. By pass all AC signal, results in increase the gain at the output. The signal source is connected to the transistor base via capacitor C1 capacitor C1 C2 prevents the loading effect between input and output.


56


57

Procedure:


Power supply is switched ON.

The input voltage is set with the help of Function Generator.

The output is measured using CRO and various output voltages are taken

for various frequencies.

Gain is calculated using the formula, Gain = 20 log (VO/VI)

The graph is drawn in the semi log sheet by taking frequency in Hz Vs

Gain in dB.

Bandwidth is calculated using formula is BW = (f 2 – f1) Hz


58

Tabulation:

Sl. No. Signal Amplitude (v) Time (ms)

Frequency (KHz)

1. Input Signal

2. Output Signal


59

Application:

It is used for audio frequency applications.

It is used as voltage amplifier.

Viva Questions:

How much amount of phase is there in common emitter amplifier?

Why you use coupling capacitors?

What is meant by loading effect?

What is band width?

Result:

Thus the Common Emitter Amplifier was constructed and tested and its frequency response was drawn.


60


61

10. RC PHASE SHIFT OSCILLATOR Aim:

To construct RC Phase Shift Oscillator and draw its wave form. Apparatus Required:


1. Transistor BC 108 1

2. Capacitor 0.1 µf 4

3. Resistor 1KΩ 470Ω 3.3k

1 1

4. RPS 0-30V 1

5 Bread board - 1

6 CRO - 1

7 Connecting wires - 1 set

Theory:

It is a circuit which self generating some waveform like sine, triangular,

and square wave etc.

It is basically an amplifier circuit with positive feedback introduced,

through the feedback components like resistance capacitance (RC),

inductance capacitance (IC) or crystal circuits are used.

In this case the CE amplifier is followed by a frequency determining

network. The R1, R2 combination provides dc potential divider bias and Ro, CE

provides temperature stability and provides ac signal degeneration. The high

pass or low pass RC - RC network may be used as positive feedback between

input and output.


62

Model Graph:

RC Phase Shift Oscillator:

Tabular Column:

Peak Voltage (v) Time in Sec (ms) Frequency = 1/t H Z

Amplitude (V)

Time (ms)


63

Procedure:

Connections are made as shown in circuit diagram. Power supply is

switched ON.

Varying the RPS and kept at a fixed voltage between 6V – 12V.

Now corresponding output is taken in CRO. The amplitude and time

are measured then the graph is drawn.

Formula:

6RC2

1F

π=

Design:

R = 200kΩ C = 100pF F=?

6RC2

1F

π=

610100102002

1123 −××××π

=

= 3.248 kHz Advantages:

Good frequency stability

Produces pure sine wave output

Disadvantages:

Very difficult to start oscillations

Not suitable for variable frequency

Not suitable for frequency oscillations


64


65

Viva Questions:

Why is an RC phase shift oscillator so called?

Mention two low frequency oscillators

Why LC oscillators are not used at audio frequencies?

What is the condition to initiate oscillations?

Result:

Thus RC Phase Shift Oscillator characteristics were drawn.


66

BF 195C

0.01µF

+

2.5kΩ

L1

5µF

VCC = 12V

L2

100 µF

5µF 33kΩ

RE

-

+

+ -

-

+ -

10KΩ 1KΩ

R2

R1 RC

V0

+10.521H 6.655H+

Hartely Oscillator:


67

11. HARTELY & COLPITTS OSCILLATOR Aim: To design construct and test a high frequency Hartely oscillator for a frequency of 400Hz & also construct & test frequency Colpitts Oscillator for a frequency of 0.5MHz. Apparatus Required:


Resistor 33KΩ, 2.5KΩ,

10KΩ, 1KΩ 1

Capacitor

5µF 100µF 100pF .1µF

2 1 2 1

Inductor 10.521H 6.655H 1.5mH

1 1 1

Transistor BF195C BC195C

1 1

RPS (0-30)V 1 CRO - 1 Bread Board - 1 Connecting Wires - -

Design Specifications:

Hartely Oscillator:

VCC = 12V,

ICQ = 2mA,

VCEQ = 5V,

F0 = 10 KHz

hfe = 50,

C = 0.1µF


68

BC 195C

1.5mH

+

2.5kΩ

-

5µF + -

100 µF

+

-

5µF + -

10KΩ 1KΩ

VCC = 12V

33kΩ

+ -

100pF 100pF

VO

Colpitts Oscillator:


69

Step: 1

To design RC & RE

VCC = VCE (Q) + ICQ (RC+RE)

RC+RE = mA2

512 −

= 3.5KΩ

Choose RE = 1KΩ

RC = 2.5KΩ

Step: 2

To design R1 & R2

VR2 = VBE + ICQ RE

= 0.7 + 2x10-3 x 1 x 10-3

VR2 = 2.7V

VR1 = VCC – VR2

= 9.3V

4.37.23.9

RR

VV

2

1

2R

1R ===

Chose R2 = 10KΩ

R1 = 33KΩ Step: 3

To design the feed back amp.

Choose f0 = 2500Hz

C = 0.01µF

.C.f.π2

1L,

.CL2π

1f 2

022eq

eq

0 ==

232 )1050.2(4

1×π

=

Leq = 405mH

Leq = L1+L2 = 405mH

Choose L1 = 400mH, L2 = 5mH


70

Tabulation:

Hartely oscillator

Peak Voltage (V) Time in sec Frequency = 1/t Hz

Colpitts oscillator

Peak Voltage ( V) Time in sec Frequency = 1/t Hz


71

Calculation Theoretical Value,

L1 = 10.521H, L2 = 6.655mH

C = 0.01µF

Leq = L1+L2 = 17.176

Hz22.384100.0117.1762π

1

.CL2π

1f

6-eq

0 =××

==

Observed frequency,

ValueacticalPr107.2

1T1

f 3p →×

== −

= 370.37Hz

Design Specification: Colpitts Oscillator:

VCC = 12V,

VCEQ = 5V,

HFE = 10,

ICQ = 2mA,

F0 = 0.5MHz,

L = 1mH Step: 1

To design RC & RE

VCC = VCEQ+ICQ (RC+RE)

mA2

512I

VVRR

CQ

CEQCCEC

−=−

=+

= 3.5KΩ

Choose RE = 11KΩ, RC = 2.5KΩ

Step: 2 To design R1 & R2

VR2 = VBE + ICQ RE

= 0.7 + 2 x 103 x 1 x 103

VR2 = 2.7V

4.3RR

VV

2

1

2R

R1 ==


72


73

Theory:

Hartely Oscillator:

The tank circuit shown in the circuit consist of two coils L1 & L2. The coil L1 is inductively coupled to the coil L2 and the combination work as an auto transformer. The feedback b/w the o/p & i/p circuits are accomplished through auto transformer action which also introduced a phase shift of 180o. The phase reversed b/w the o/p & i/p voltages occur because they are taken from the opposite ends of the coils (L1 & L2) with respect to the tap which is

grounded. The frequency of oscillator is grounded byC.L2

1F

eq

O π= .

Colpitts Oscillator:

Colpitts oscillator is a radio frequency oscillator which generates a frequency of the range of (30 KHz to 30MHz). The collector supply voltage VCC is applied to the collector transistor RC parallel combination of RE = CE with resistor R1 = R2 provides the stabilized self bias. The tuned circuit consists of C1, C2 & L are extending from collector act to the base act determines basically the transistor of oscillator. The feedback is through the tank circuit it self. Procedure:

Connections are made as per the circuit diagram. The o/p waveform is traced. From the observation the frequency of oscillation is determined and is compared with the theoretical frequency.

Result:

Thus the Hartely oscillator is designed & tested for a frequency of 2500Hz and wave form is traced. Viva Question:

1. Difference between Hartely and Colpitts oscillator?

2. Application of Hartely and colpitts oscillator?


74

S

D

G

Characteristics of JFET:

Circuit Diagram:

Pin Details:

V V

A

470Ω

1.2Ω

(0-5) V (0-30) V

RPS (0-30) V

RPS (0-30) V

VDS VGS

G

+ -

+

- +

- +

-

BFW11

D

S

(0-10) mA


75

12. CHARACTERISTICS OF JFET

Aim : To draw the drain and transfer characteristics of JFET and determine the pinch off voltage. Apparatus Required :

S. No Apparatus Name Range Quantity 1. RPS (0-30)V 1

2. Resistors 1.2KΩ, 470Ω 2

3. Ammeter (0-10) mA 1

4. Voltmeters (0-30)V, (0-5)V 2

5. JFET BFW11 1

6. Breadboard - 1

7. Connecting wires - 1set

Theory:

A junction field effect transistor is a three terminal semiconductor device

in which current conduction is done by one type of carrier i.e. electrons and

holes.

It acts like a voltage controlled device that means input voltage (VGS)

controls the output current (ID).

Model Calculation:

IDSS = 32mA, VGS = - 4.5V, VGS (OFF) = - 8V ID =?

ID = 2

GS(OFF)

GSDSS V

V1I

−×

=

−−8-

1 )5.4(32

ID = 6.12mA


76

Model Graph:

Drain Characteristics:

Transfer Characteristics:


77

Procedure :



• The voltage (VGS) is kept constant by varying RPS1 and voltage

across drain and source (VDS) and corresponding ammeter

readings are noted and tabulated.

• The process is repeated for two more constant VGS values and

the corresponding readings are noted and tabulated.



• The voltage (VDS) is kept constant by varying RPS2 and voltage

across gate and source (VGS) and corresponding ammeter

readings are noted and tabulated.

Circuit Design:

ID = 2

GS(OFF)

GSDSS V

V1I

−×

ID = Drain current at given VGS

IDSS = Drain – source saturation current

VGS = Gate - source voltage

VGS (OFF) = Gate - source cut off voltage

Drain Resistance = D

DS

IV∆

∆

∆VDS = Changes in drain – source voltage

∆ ID = Changes in drain current


78

Tabulation :


S. No VGS = 0V VGS = 0.5V VGS = 1V

VDS (V) ID (mA) VDS (V) ID (mA) VDS (V) ID (mA)


S. No VDS = VP = 4v

VGS(V) ID(mA)


79

Precaution:

• First identify the terminals namely, gate, drain, source then connects

the FET in the circuit.

• Gate is always reverse biased. Graph:

Drain Characteristics

The graph is drawn between the drain current (ID) and VDS at constant VGS.


The graph is drawn between ID and gate-source voltage (VGS) at

constant VDS is known as transfer characteristics.

Result :

Thus the drain and transfer characteristics of JFET were obtained

and the pinch off voltage when VGS is zero ………………..

VP at VGS = 0.5V ……………….

VP at VGS = 1V ………………. Applications :

• It is used as a buffer amplifier because of its high input impedance

and low output impedance.

• It is used in phase shift oscillators to minimize the loading effect.

• It is used as RF amplifier in receivers.

Viva Questions :

• What is the difference between JFET and BJT?

• Mention the name of the FET terminals?

• What is meant by drain resistance?

• What is meant by pinch – off voltage?

• Why FET is called as a unipolar device?


80


81

13. COMMON SOURCE AMPLIFIER

Aim:

To construct the Common Source Amplifier and draw its frequency response curve. Apparatus Required:

S. No. Apparatus Required Range Quantity 1. FET BFW11 1

2. Capacitor 470µF 100 µF/25V

1 2

3. Resistor 1.5 KΩ 1 KΩ

1 1

4. FGR - 1

5. Power supply (0 – 30)Volts 1

6. CRO - 1

7. Bread Board - 1

8 Connecting Wires - 1set Theory:

An A.C signal is applied into the gate which results in the variation of VGS. This produces a sinusoidal drain current. As this drain current flows through the drain resistor, an amplified AC voltage is available at output. Here the resistors R1 and R2 are used to bias the field effect transistor. The capacitor are coupling capacitors. C1 is used to couple the AC input voltage and C2 is used to couple output voltage. As the Gate source voltage increases, the drain current also increases. As a result of this, the voltage drop across the resistor (RD) also increases. This causes the drain voltage to decrease. It means that the positive half cycle of the input voltage produces the negative half cycle of the output voltage.


82


83

Procedure:


The input voltage is set with the help of Function generator.

Now power supply is switched ON.

The output is measured using CRO.

By adjusting the frequency of function generator, the output

voltages are noted in the CRO.

This procedure is followed to take atleast 10 readings.

The graph is drawn in semilog graph sheet (Frequency Vs Gain).

Bandwidth is calculated by using the formula is f2 – f1.


84

Tabulation:

Signal Time in (ms) Amplitude in (v) Frequency (HZ)

Input Signal

Output Signal


85

Result:

Thus the Common Source Amplifier was constructed and tested and its output waveform was drawn.


86

Characteristics of UJT:

Circuit Diagram:

Pin Details:

V V

A

470Ω

470Ω

(0-15) V (0-15) V

RPS (0-30) V

RPS (0-30) V

2N2646

VB182

VE

IE E

+ -

+

-

+

-

+

-

B2

B1

B1

B2

E


87

14. CHARACTERISTICS OF UJT

Aim:

To draw the V-I characteristics of UJT and find the peak point voltage. Apparatus Required:

S. No Apparatus Name Range Quantity

1. RPS (0-30)V 2

2. Resistor 470Ω 2

3. Ammeter (0-50)mA 1

4. voltmeter (0-15)V 2

5. UJT 2N2646 1

6. Breadboard -- 1

7. Connecting wires -- 1set

Theory:

Uni Junction Transistor (UJT) is a three terminal semiconductor switching device. It has only one PN junction. It has no ability for amplification while it has ability to control the AC power with a small gain. It exhibits a negative resistance characteristics and hence it can be used as a oscillator.


88

Model Graph:


89

Procedure:


• The voltage (VB1B2) is kept constant by varying RPS and emitter

voltage (VE) and corresponding ammeter reading (IE) are noted and

tabulated.

• The process is repeated for two more constant VB1B2 values and the

corresponding readings are noted and tabulated.

Circuit Design:

1. When no voltage applied to the UJT, the interbase resistance is given by RBB = RB1 + RB2 2. If a voltage VBB is applied between the bases with emitter open. The voltage will divide up across RB1 and RB2

Voltage across RB1, BB2B1B

1B1 V

)RR(R

V ×+

=

η = )RR(

RVV

2B1B

1B

BB

1

+=

η = Intrinsic stand off ratio

V1 = η VBB

3. If rising positive voltage is applied to the emitter, the diode become forward biased when input voltage exceeds η VBB by VD.

VP = η VBB + VD

Where VP = Peak point voltage

VD = Forward voltage drop across the

Diode (for silicon = 0.7 V). Model Calculation :

VBB = 10V, η = 0.65, VD = 0.7 V

Stand off voltage V1 = η VBB

= 0.65 × 10

= 6.5 V

Peak point voltage VP = η VBB + VD

= 6.5 V + 0.7 V

= 7.2 V


90

Tabulation:

S. No VB1B2 = 4V VB1B2 = 7V VB1B2 = 10V

VE (V) IE (mA) VE (V) IE (mA) V E (V) IE (mA)


91

Precaution:

• First identify the terminals namely emitter, base1, base2.

• The emitter region is closer to base2 terminal than base1.

Graph:

Emitter voltage (VE) is taken along y-axis and emitter current (IE) is taken along x-axis. Result: Thus the characteristics of UJT was obtained and peak point voltage was determined and graph was drawn. Peak point voltage = ………………………… Applications :

• UJT is used extensively in oscillator, pulse and voltage sensing

circuits.

• It is used in relaxation oscillator to generate Sawtooth output.

• It is used as a over voltage detector. Viva Questions:

• Why it is called unijunction transistor?

• Mention the other name for diode?

• What is peak point and peak value voltage?

• Why it is called double_ based diode?

• When the temperature increases, what will happen the value of inter-

base resistance?


92

UJT RELAXATION OSCILLATOR

Circuit Diagram:


93

15. UJT RELAXATION OSCILLATOR

Aim:

To construct a relaxation oscillator using UJT & trace the wave form & also measure the frequency. Apparatus Required:

Apparatus Range Quantity RPS (0-30) V 1 CRO (0-20) MHz 1 UJT 2 N 2160 1

Capacitor 1 µF 1 Resistor 10 KΩ, 100Ω, 220Ω 1

Bread Board - 1 Connecting wires - Needed

Precautions:

1. Never temper with CRO 2. Oscilloscope should not be exposed long in moisture & high

temperature. 3. Oscilloscope should not be overloaded. 4. Oscilloscope should not be over bright. 5. Handle all the controls carefully. 6. It should be noted that generators always deliver an output but

never take input & hence care should be taken that no input is given in any form to the output ports.

7. The ventilation holes must not be covered. 8. If condensed water exists in the instruments it should be

acclimatized before switching on. 9. The instruments should be kept in a clean & dry room as must not

be operated in explosive, corrosive, dusty. 10. The display can only be cleaned with water or washing benzene

(not with spirit).


94

Model Graph:

Tabulation:

Signal Amplitude (Volts) Time (ms)

SAW TOOTH WAVE

Output A

mpl

itude

(V

olts

)

Time (ms)


95

11. All the measuring terminals are to be connected to the protective earth contact of the inlet.

12. The mains plug shall only be inserted in a socket outlet connected with protective earth contact.

13. The protective action must not be negated by the use of an extension cord without a protective conductor.

14. Any interruptions of the protection conductors inside or outside the instruments or disconnections of the protective earth terminals are likely to make the instruments dangerous. The main plug should be inserted before connections are mode to test circuits.

15. All the connections should be tight. 16. Power supply should not be overloaded. 17. Don’t vary the supply suddenly.

Procedure:

1. Rig up the circuit as per the circuit diagram. 2. Set VBB = 10 V (say) (Supply voltage normally used lies in the

range 10 to 35 V). 3. Connect CRO across capacitor. 4. Switch on the power supply set VBB = 10V & observe the wave

form on the CRO. 5. Note down the practical frequency. 6. Switch off the supply. 7. Connect CRO across R1 switch on the supply & observe the wave

forms. 8. Note down the practical frequency.

Application:

1. Pulse generator for firing SCR. 2. In the negative resistance region, if can be operated as a

relaxation oscillator. 3. Used as a fast acting switching. 4. Used as fine wave generator, square wave generators, saw-toot

generators. 5. Used in time delay circuits. 6. Used in TV. 7. Used in radar equipment. 8. Used in oscilloscope.

Employment:

• TV assembler. • This skill used for army. • Oscilloscope assembler industry.


96


97

Viva questions:

1. What is the function oscillator?

2. Which portion of the characteristics used in a relaxation

oscillator?

3. Which oscillator is very suitable for audio range applications?

4. Which oscillator is suitable for RF range application?

5. How does oscillation start in oscillators?

6. What is the difference between oscillator & amplifier?

7. How many classification oscillators?

8. What are types of oscillator based on frequency generator?

9. What is crystal oscillator?

10. Define intrinsic stand-off ratio?

11. How the frequency of oscillation determined in theoretical?

12. How many terminals in the UJT?

13. What are the types of three region names?

14. Which Condition of region the UJT is off state?

15. When the UJT is ON? Which region?

16. What is negative resistance region?


98

Characteristics of SCR: Circuit Diagram: Pin Details:

K A G

TYN 604

-

K (0-30) mA

A

IN 4001

TYN 604

RPS (0-30) V

10Ω

IG

A

+

+

-

G + -

330Ω

RPS (0-30) V

(0-100) mA

K

A

+ -

+

-

(0-25) V

A

V

Ih


99

16. CHARACTERISTICS OF SCR

Aim:

To obtain the V-I characteristics of SCR and find the break over voltage and holding current. Apparatus Required:

Theory:

A silicon controlled rectifier (SCR) is a semiconductor device that acts as a true electronic switch. It can change the alternating current in to direct current. It can control the amount of power fed to the load. Thus the SCR combines the features of rectifier and a transistor.

If the supply voltage is less than the break over voltage, the gate will open (IG = 0). Then increase the supply voltage from zero, a point is reached when the SCR starts conducting. Under this condition, the voltage across the SCR suddenly drop and most of the supply voltage appears across the load resistance RL. If proper gate current is made to flow the SCR can close at much smaller supply voltage.

S. No Name of the Apparatus Range Quantity 1. SCR TYN 604 1 2. RPS (0-30)v 2 3. Resistor 330Ω 1 4. Diode IN4001 1 5. Voltmeter (0-30)v 1 6. Ammeter (0-10) mA 1 7. Ammeter (0-100)mA 1 8. Resistor 10Ω 1 9. Bread board -- 1 10. Connecting wires -- 1set


100

IA (

mA

)

VAK (Volts)

Ig= Ig=

Model Graph:


101

Procedure:

• The connections are made as per in the circuit diagram.

• First by varying RPS 2 then gate current (IG) is kept constant.

• The voltage between anode and cathode is increased in step by

step by varying the RPS 1.

• The corresponding anode current (IA) is noted.

• The process is repeated for two more constant value of IG, the readings are tabulated.

Circuit Design:

VS = IM×RS + VAK

IM = S

AKS

R)V(V −

Where

IM = maximum current through the SCR

VS = supply voltage

VAK = voltage between anode and cathode

RS = current limiting resistor

Model Calculation:

VS = 30V RS = 330Ω

VAK = 1V IM =?

IM = S

AKS

R)V(V −

= mA87330

)1(30 =−


102

Tabulation:

S. No Anode-Cathode Voltage V ak (Volts)

Gate Current Ig (mA)

Anode Current Ia (mA)

Anode – Cathode volt when SCR in

ON (volts)


103

Graph:

The graph is drawn by taking voltage between anode and cathode (VAK) along x-axis and anode current along y-axis. Precaution:

First identify the terminals that means namely cathode, anode,

gate then connect the SCR in the circuit

Gate current is always in minimum to turn on the SCR.

The supply voltage is less than the break over voltage of the SCR.

Result:

Thus the V-I characteristics of SCR was obtained and graph was drawn. Application :

It is used to control the speed of the motor.

It is used as a static contactor.

AC and DC circuit breaker.

It is used in over light detector.

It is used in battery chargers. Viva questions:

How many terminals are in SCR? Mention it.

Mention any two methods to turn off the SCR?

What is meant by break over voltage?

Mention the other name of SCR’s are available in market?

What is meant by holding current and latching current?

Why it is called as silicon controlled rectifier?


104

Characteristics of Diac:

Circuit Diagram:

Forward Direction:

Reverse Direction:

MT2

MT1

(0-100) mA 5KΩ/5W

RPS (0-300) V

(0-50) V

+

-

+ -

+

-

V

A


105

17. DIAC & TRIAC CHARACTERISTICS

Aim:

To draw the V-I characteristics of DIAC & TRIAC and obtain the break over voltage (VBO). Apparatus required:

S. No Apparatus Name Range Quantity 1 Resistor 5kΩ / 5w 1 2 Resistor 1kΩ 2 3 RPS (0-300) V 1 4 RPS (0-30) V 2 5 Voltmeter (0-50) V 1 6 Voltmeter (0-15) V 1 7 DIAC SSD3A 1 8 TRIAC BTM36 1 9 Ammeter (0-50) mA 1

10 Ammeter (0-30) mA 1 11 Ammeter (0-10) mA 1 12 Breadboard - 1 13 Wires - 1set

Theory:

A DIAC is a two terminal three layer bidirectional device which can be switched from its off state to on state for either polarity of applied voltage. The operation of DIAC is identical both in forward and reverse conduction. The DIAC does not conduct until the applied voltage of either polarity reaches the break over voltage VBO. A TRIAC is a three terminal semiconductor switching device which can control alternating current in a load. A TRIAC can control conduction of both positive and negative half cycles of A.C supply. It is sometimes called a bidirectional semiconductor triode switch.


106

Characteristics of Triac:

Forward Direction:

Reverse Direction:

A

V A

(0-50) mA

(0-50) mA RPS

(0-30) V

(0-15) V

RPS (0-30) V

MT1

MT2

IG

1KΩ

1KΩ

IMT2

+

+ +

+

+

-

-

- -

-

G

A

V A

(0-50) mA

(0-50) mA RPS

(0-30) V

(0-15) V

RPS (0-30) V

MT1

MT2

IG

1KΩ/5W

1KΩ

IMT2

+

+

+

+

+

-

-

-

-

-

G

BT136

G


107

Procedure: Diac Characteristics:

o The connections are made as shown in the circuit diagram. o First DIAC is connected in forward direction o The input supply is increased in step by step by varying the RPS o The corresponding ammeter and voltmeter readings are noted

and tabulated. o Then the DIAC is connected in reverse condition. o The above process is repeated.

Triac Characteristics:

• The connections are made as shown in the circuit diagram. • The TRIAC is connected in forward direction and supply is

switched ‘ON’. • VMT1MT2 is constant by varying RPS2 and then varying IG by

varying RPS1. • The corresponding ammeter and voltmeter readings are noted

and tabulated. • Next the TRIAC is connected in reverse direction. • The above process is repeated.

Graph:

Voltage is taken along x-axis and current is taken along y-axis.


108

- VB0

+ VB0

Model Graph:

Diac Characteristics:

Model Graph:


109

Result:

Thus the V-I characteristics of DIAC & TRIAC was obtained and graph was drawn. Break over voltage in forward direction of DIAC (VBO) = ……….… Break over voltage in reverse direction of DIAC (VBO) = …….……

Break over voltage in forward direction of TRIAC (VBO) = …….…… Break over voltage in reverse direction of TRIAC (VBO) = …….……

Applications:

Diac:

It is used in lamp dimmer It is used in heat control It is used as a switching device to trigger TRIAC It is used for the speed control of universal motor


110

Tabulation:

Diac Characteristics:

S. No Forward direction Reverse direction

Voltage(volts) Current (ma) Voltage(volts) Current(ma)

Triac Characteristics:

Forward Direction:

S. No VMT1MT2 (V) when Triac

is ‘OFF’ IG (mA)

VMT1MT2

when Triac is ‘ON’

IMT2 (mA)

Reverse Direction:

S. No VMT2MT1(V)

when Triac is ‘OFF’

IG (mA) VMT2MT1

when Triac is ‘ON’

IMT2 (mA)


111

Triac: It is used in phase control. It is used in motor speed control. It is used as a high power lamp switch. It is used for light control. It is used to control the A.C power fed in to a load.

Viva Questions:

• Give one example for bidirectional device? • What is the abbreviation of DIAC? • How many PN junctions are in DIAC? • Mention the terminals of DIAC? • Mention any two application of DIAC? • How many terminals are there in TRIAC? • What are applications of TRIAC? • What is the difference between the SCR and TRIAC? • Give one example for TRIAC? • How many semiconductor layers are there in TRIAC?


112


113

18. CLIPPER, CLAMPER & VOLTAGE DOUBLER Aim:

To construct and study the output wave form of Clipper, Clamper Circuit and also determine regulation characteristics of voltage doubler. Apparatus Required:

S. No. Apparatus Required Range Quantity 1. RPS (0 – 30) V 1

2. Transformer (6-0-6) V 1

3. Diode IN4001 2

4. Capacitor 100 µF 1

5. Resistor 10 KΩ, 100KΩ

1 1

6. DC Voltmeter (0-30) V 1


8. CRO -- 1

9. FGR -- 1

10. Bread Board -- 1

11. Connecting Wires -- 15 Theory:

Clipper

The clipping circuit requires a minimum of two components i.e. a diode and a resistor. DC battery is also used to fix the clipping level. The input waveform can be clipped by interchanging the position of various elements.


114


115

Clamper:

Clamping is the process of introducing a dc level into an ac signal. Clampers are also sometimes known as dc restorers. Clamping is the process of shifting the input signal above or below the zero level. A clamping circuit should not change peak to peak value of the signal; it should only change the DC level. To do so, a clamping circuit uses a capacitor together with a diode and a resistor. Voltage Doubler:

Formula:

100

Load

Full

VLoad

Full

VLoad

NoV

Regulation

Voltage

of

% ×−

=

It is a clamper circuit. A voltage doubling circuit produces an output voltage which is approximately double the peak voltage of the input waveform. When the point ‘A’ is positive with respect to point ‘B’ diode D1 conducts and capacitor C1 is charged to the maximum voltage Vm of the applied A.C voltage in the polarity. When the point ‘B’ is positive relative to point A, diode D2 conducts and capacitor C2 is charged to the maximum voltage. Em in the polarity shown.


116

Circuit Diagram of Positive Clamper: Circuit Diagram of Negative Clamper:

- +

100 KΩ

100 µF

IN 4001 K

A

FGR CRO

CRO

100 µF

FGR 100 KΩ

K

IN 4001

- +


117

Procedure:

Clipper & Clamper:

Connections are made as shown in fig.

Power supply is switched ON.

Using Function Generator we can vary the frequency and fixed at

particular frequency.

Now the corresponding input and output waveforms are drawn.

Amplitude and time, input & output waveforms are drawn.

And graph is drawn to input and output waveform.

Power supply is switched OFF.

Voltage Doubler:

Connections are made as shown in the circuit diagram.

Power supply is switched ON

The full load is applied until the ammeter shows the rated value

Remove the load and take ammeter , voltmeter readings

Varying the Rheostat load at various point at ammeter ant

corresponding reading are taken and tabulated

Graph is plotted between dc current and dc voltage reading.


118

Model Graph:

Positive Clamper:

Negative Clamper:

Time (ms)

Time (ms)

Amplitude (v)

2Vm

Vm

Amplitude (v)

Time (ms)

Time (ms)

-Vm

-2Vm


119

Application:

Clipper:

It is used in radar applications.

Used in digital computers.

Widely used in radio and television receivers.

Clamper:

Used in television receivers to restore the original D.C reference

signal to the video signal.

Used to produce a D.C voltage whose value is multiple of peak

AC input applied voltage.

Voltage Doubler:

Used in AC and DC radio receivers.

Used in other devices where use of power transformer is not

permitted.

Used in power supplies for X ray tubes.


120


121

Viva Questions:

What is clipper?

What is meant by biased clipper?

Mention the application of clipper?

Differentiate between series and shunt positive clipper?

What is the other name for clamper?

What is clamper?

Mention the application of clamper?

What is the difference between the clipper and clamper?


122

Tabulation:-

Signal Input Signal Output Signal

Amplitude (v) Time (ms) Amplitude (v) Time (ms)

Model Graph

VDC (V)

I DC (

mA

)


123

Result:

Thus the characteristics of Clipper, Clamper & Voltage Doubler Circuits were constructed and studied and its input and output waveforms were drawn.


124

Circuit Diagram:

Light Dependent Resistor:

Photo – Diode:


125

19. LDR, PHOTODIODE AND PHOTOTRANSISTOR CHARACTERISTICS

Aim: To study of photo-detector’s characteristics.

1. Light dependent resistor. 2. Photo-diode. 3. Photo-transistor.

Apparatus Required:


1. Power supply (0-30) V 2


3. Voltmeter (0-10) V (0-30) V

1 1

4. Resistor 680Ω 1KΩ

1 1

5. Breadboard - 1

6. Connecting wires - 10

7. LDR

Photo diode Photo transistor

- 1 1 1

Procedure

Photo diode

1. Connect the circuit as per the circuit diagram.

2. Maintain a known distance 9say 5cm) between the DC bulb and the

LDR.

3. Set the voltage of the bulb (say 2 V), vary the voltage of the diode in

steps of 1 V and note down the corresponding diode current Ir.

4. Repeat the above procedure for VD = 4V, 6V, etc.

5. Plot the graph: VD vs Ir for a constant VL.


126

Photo – Transistor:

Tabular Column : LDR

Distance (cm) Current (µA)

Photo Diode:



127

Repeat the photo-diode experimental procedure for p hoto-transistor

also.

Light Dependent Resistor:

1. Connect the circuit as per the circuit diagram.

2. Maintain a known distance between the DC bulb and the LDR.

3. Vary the voltage of the bulb in steps of 1 V and note down the

resistance value across the LDR using multimeter.

4. Plot the graph: V vs I.

Application:

• It is used in alarm circuits.

• It is used to count items on a conveyor belt.

• It is also used in demodulation, logic circuits, optical communication

systems, character recognition etc.

Viva Questions:

• How does photo diode work?

• Give two applications of photo diode?

• Which biasing is suitable for photo diode application?

• What is meant by dark current?

• What is meant by dark resistance?


128

Photo Transistor:


Model Graph:


129

Result:

Thus the following characteristics of LDR, Photo diode & Photo

Transistor was obtained and graph was drawn.


130

Model Graph

Solar cell


131

20. SOLAR CELL AND OPTO COUPLER

Aim:

To draw the V-I Characteristics curve for the given Solar cell. Apparatus required:

S. No. Apparatus Required Range Quantity 1 Opto coupler 4N26 1 2 Ammeter (0-30) mA 1 3 Resistor 10 Ω, 470 Ω 1 4 RPS (0-30) V 1 5 RPS (0-5) V 1 6 Bread Board - 1 7 Connecting wire - - 8 Solar Cell - 1

Theory:

Solar cell:

A solar cell or solar battery is basically a PN junction diode which converts solar energy into electrical energy. It is also called a solar energy converter and is simply a photo diode operated at zero bias voltage. Opto coupler:

Optocoupler is a device that uses light to couple a signal from its input to its output. The LED is on the left and the transistor is on the right. When the LED is energized, current flows through the LED. The light from the LED hits the transistor and sets up a reverse current. The output current depends on the reverse current.


132

Opto Coupler

Model Graph:


133

Procedure:

Opto Coupler:

1. Connect the circuit as per the circuit diagram. 2. Vary the voltage and note down the current value at input and output side. 3. Plot the graph IF vs IB

Solar Cell:

1. Connect the circuit as per the circuit diagram. 2. Maintain a known distance between the DC bulb and the solar Cell. 3. Set the voltage of the bulb vary the voltage and note down the current. 4. Plot the graph V vs I.

Result:

Thus the characteristic curve of solar cell and opto coupler were drawn.


134

Tabular Column:

Solar Cell:

Distance in cm Current in mA

Opto Coupler:

Distance in cm Current in mA


135

Application:

1. Solar cells are used as secondary power source in satellite and space

vehicles.

2. They are used to charge storage batteries.

3. They are used for household purpose.

Viva Question

1. What is solar Cell?

2. What is opto coupler?

3. What is the uses of the Solar Cell?

4. What is the uses of the Opto Coupler?


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137

EXTRA SYLLABUS

21. ASTABLE MULTIVIBRATOR

Aim:

To construct the Astable Multivibrator using IC 555 Timer and draw its output waveforms. Apparatus Required:


1. Timer IC 555 1

2. Capacitor 0.1 mF

0.01 mF/25V 1 1

3. Resistor 10 KΩ 2

4. RPS (0 – 5) V 1

5. CRO -- 1

6. Bread Board -- 1


Theory:

An Astable Multivibrator is also known as free running Multivibrator, generates a square waveform of known period. It does not have any permanent stable states. The circuit changes the state continuously from one quasi stable state to the other after a predetermined length of time and it does not require any external input.


138


139

Procedure:

Connections are made as shown in fig. and Power Supply is

switched ON.

The output square wave is measured from pin number 3 and GND.

The Ramp output is measured across the capacitor i.e. pin number 6

and GND.

Waveforms are measured in CRO.

The graph is drawn for both square waveforms as well as saw tooth

waveform.

Design:

Duty cycle = 20% TI=0.69 ON period T1 = 1ms, frequency =?

21

1

TT

TCycleDuty

+=

21

3

TT101

10020

+×=

−

T1 +T2 = 5ms

T1

fFrequency =

3105

1F −×

=

= 200Hz

Application:

Oscillators

Timing circuits

Square wave generators


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141

Viva Questions:

1. What is meant by duty cycle?

2. Tell two commercial applications of 555 timer?

3. Which waveforms are generated by 555 timer?

4. How will you control the duty cycle?

Result:

Thus the Astable Multivibrator constructed using IC 555 Timer. Output waveforms were taken and drawn.

EDC LAB Manual

Documents

edc lab manual

protection

protective

condensed

full wave

horizontal

half wave

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