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
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
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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
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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:
+
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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
-
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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
)
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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.
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Tabulation:
Reverse Bias:
S. No Voltage In Volts (V R) Current In µA (IR)
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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?
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Characteristics of Zener Diode:
Circuit Diagram:
Forward Bias:
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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
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Reverse Bias:
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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 connections are made as shown in the circuit diagram.
• 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.
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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)
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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 = ----------------
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Tabulation:
Reverse Bias:
S. No Reverse Voltage in Volts (V) Reverse Current in (mA)
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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?
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Half Wave Rectifier (Without Filter Circuit)
Half Wave Rectifier (With Filter Circuit)
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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.
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CRO 230 V AC Supply
2K
9V
A K
K A
9V
Full Wave Rectifier (Without Filter Circuit)
Full Wave Rectifier (With Filter Circuit)
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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.
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Half wave Rectifier Tabulation:
Description Amplitude (V) Time Period
Input voltage waveform
Output voltage waveform without filter
Output voltage waveform with filter
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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.
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Full wave Rectifier Circuit Tabulation:
Description Amplitude (V) Time Period
Input voltage waveform
Output voltage waveform without filter
Output voltage waveform with filter
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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?
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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.
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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.
`
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ModelGraph:
Tabular Column:
S. No Description Amplitude (v) Time Period (ms)
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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
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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.
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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.
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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)
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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.
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Series Voltage Regulator
Vo (V)
Vin(V)
Vo (V)
Rv (KΩ)
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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 ____________ %.
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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
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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 =
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Input Characteristics:
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)
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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:
Input Characteristics:
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.
Output Characteristics:
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.
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Tabulation:
Input Characteristics:
S. No VCE=0V VCE=5V VCE =10V
VBE(V) IB(µA) VBE(V) IB(µA) VBE(V) IB(µA)
Tabulation:
Output Characteristics:
S. No IB=40µA IB=60µA IB=80µA
VCE (V) IC (mA) VCE (V) IC (mA) VCE (V) IC (mA)
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Graph:
Input Characteristics:
Base current (IB) is taken along y-axis, base-emitter voltage (VBE) is
taken along x-axis.
Output Characteristics:
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?
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RC Coupled Amplifier:
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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).
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Model Graph:
3 dB
F1 Low F2 High FREQUENCY (HZ)
GA
IN (
DB
)
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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.
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Tabulation:
Frequency (Hz) Voltage (V) Gain Vo/Vi Gain db 20 log
Vo/Vi
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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?
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Emitter Follower:
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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.
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Tabulation:
Sl. No. Frequency in Hz Output Voltage V O
(volts) Gain in dB = 20 log
(VO/Vi)
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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?
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9. COMMON EMITTER AMPLIFIER Aim:
To construct Common Emitter Amplifier and draw its frequency response curve. Apparatus Required:
S. No. Apparatus Required Range Quantity
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
8. Connecting Wires -- 15
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.
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Procedure:
Connections are made as shown in circuit diagram.
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
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Tabulation:
Sl. No. Signal Amplitude (v) Time (ms)
Frequency (KHz)
1. Input Signal
2. Output Signal
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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.
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10. RC PHASE SHIFT OSCILLATOR Aim:
To construct RC Phase Shift Oscillator and draw its wave form. Apparatus Required:
S. No. Apparatus Required Range Quantity
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.
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Model Graph:
RC Phase Shift Oscillator:
Tabular Column:
Peak Voltage (v) Time in Sec (ms) Frequency = 1/t H Z
Amplitude (V)
Time (ms)
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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
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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.
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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:
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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:
S. No. Apparatus Required Range Quantity
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
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BC 195C
1.5mH
+
2.5kΩ
-
5µF + -
100 µF
+
-
5µF + -
10KΩ 1KΩ
VCC = 12V
33kΩ
+ -
100pF 100pF
VO
Colpitts Oscillator:
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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
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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
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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 ==
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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?
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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
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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
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Model Graph:
Drain Characteristics:
Transfer Characteristics:
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Procedure :
Drain Characteristics:
• The connections are made as shown in the circuit diagram.
• 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.
Transfer Characteristics:
• The connections are made as shown in the circuit diagram.
• 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
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Tabulation :
Drain Characteristics:
S. No VGS = 0V VGS = 0.5V VGS = 1V
VDS (V) ID (mA) VDS (V) ID (mA) VDS (V) ID (mA)
Transfer Characteristics:
S. No VDS = VP = 4v
VGS(V) ID(mA)
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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.
Transfer Characteristics:
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?
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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.
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Procedure:
Connections are made as shown in circuit diagram.
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.
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Tabulation:
Signal Time in (ms) Amplitude in (v) Frequency (HZ)
Input Signal
Output Signal
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Result:
Thus the Common Source Amplifier was constructed and tested and its output waveform was drawn.
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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
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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.
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Model Graph:
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Procedure:
• The connections are made as shown in the circuit diagram.
• 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
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Tabulation:
S. No VB1B2 = 4V VB1B2 = 7V VB1B2 = 10V
VE (V) IE (mA) VE (V) IE (mA) V E (V) IE (mA)
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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?
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UJT RELAXATION OSCILLATOR
Circuit Diagram:
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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).
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Model Graph:
Tabulation:
Signal Amplitude (Volts) Time (ms)
SAW TOOTH WAVE
Output A
mpl
itude
(V
olts
)
Time (ms)
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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.
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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?
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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
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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
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IA (
mA
)
VAK (Volts)
Ig= Ig=
Model Graph:
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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 =−
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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)
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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?
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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
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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.
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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
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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.
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- VB0
+ VB0
Model Graph:
Diac Characteristics:
Model Graph:
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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
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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)
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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?
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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
7. Ammeter (0-50) mA 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.
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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.
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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
- +
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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.
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Model Graph:
Positive Clamper:
Negative Clamper:
Time (ms)
Time (ms)
Amplitude (v)
2Vm
Vm
Amplitude (v)
Time (ms)
Time (ms)
-Vm
-2Vm
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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.
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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?
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Tabulation:-
Signal Input Signal Output Signal
Amplitude (v) Time (ms) Amplitude (v) Time (ms)
Model Graph
VDC (V)
I DC (
mA
)
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Result:
Thus the characteristics of Clipper, Clamper & Voltage Doubler Circuits were constructed and studied and its input and output waveforms were drawn.
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Circuit Diagram:
Light Dependent Resistor:
Photo – Diode:
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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:
S. No. Apparatus Required Range Quantity
1. Power supply (0-30) V 2
2. Ammeter (0-10) mA 1
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.
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Photo – Transistor:
Tabular Column : LDR
Distance (cm) Current (µA)
Photo Diode:
Distance (cm) Current (µA)
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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?
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Photo Transistor:
Distance (cm) Current (µA)
Model Graph:
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Result:
Thus the following characteristics of LDR, Photo diode & Photo
Transistor was obtained and graph was drawn.
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Model Graph
Solar cell
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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.
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Opto Coupler
Model Graph:
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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.
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Tabular Column:
Solar Cell:
Distance in cm Current in mA
Opto Coupler:
Distance in cm Current in mA
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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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EXTRA SYLLABUS
21. ASTABLE MULTIVIBRATOR
Aim:
To construct the Astable Multivibrator using IC 555 Timer and draw its output waveforms. Apparatus Required:
S. No. Apparatus Required Range Quantity
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
7. Connecting Wires -- 15
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.
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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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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.
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