Electronic Devices and Instrumentation Lab [18ECL37]

Course Learning Objectives:

This laboratory course enables students to
 Understand the circuit schematic and its working.
 Study the characteristics of different electronic devices.
 Design and test simple electronic circuits as per the specifications using discrete electronic
components.
 Familiarize with EDA software which can be used for electronic circuit simulation.

PART A : Experiments using Discrete components

1. Conduct experiment to test diode clipping (single/double ended) and clamping circuits
(positive/negative).
2. Half wave rectifier and Full wave rectifier with and without filter and measure the ripple factor.
3. Characteristics of Zener diode and design a Simple Zener voltage regulator determine line and load
regulation.
4. Characteristics of LDR and Photo diode and turn on an LED using LDR
5. Static characteristics of SCR.
6. SCR Controlled HWR and FWR using RC triggering circuit
7. Measurement of Resistance using Wheatstone and Kelvin’s bridge.
PART-B : Simulation using EDA software (EDWinXP, PSpice, MultiSim, Proteus, Circuit Lab or
any equivalent tool)
1. Input and Output characteristics of BJT Common emitter configuration and evaluation of parameters.
2. Transfer and drain characteristics of a JFET and MOSFET.
3. UJT triggering circuit for Controlled Full wave Rectifier.
4. Design and simulation of Regulated power supply.

Course Outcomes:
On the completion of this laboratory course, the students will be able to:
 Understand the characteristics of various electronic devices and measurement of parameters.
 Design and test simple electronic circuits.
 Use of circuit simulation software for the implementation and characterization of electronic circuits
and devices.

1. David A Bell, “Fundamentals of Electronic Devices and Circuits Lab Manual, 5th Edition, 2009, Oxford
University Press.
2. Muhammed H Rashid, “Introduction to PSpice using OrCAD for circuits and electronics”, 3rd Edition,
Prentice Hall, 2003.

1
Electronic Devices and Instrumentation Lab [18ECL37]

Experiment No. : 01
Diode clipping (single/double ended) and clamping circuits (positive/negative)
AIM: Conduct experiment to test diode clipping (single/double ended) and clamping circuits
(positive/negative).
Components required: - Switching diode – 1N4007, Resistors 10K/1k Signal generator, Variable DC
supply Capacitor 1uf/10uf 20V, bread board, Wires, CRO & multimeter for testing

Working of Clipper Circuit

The clipper circuit can be designed by utilizing both the  linear and nonlinear elements such as resistors,
diodes or transistors. As these circuits are used only for clipping input waveform as per the requirement
and for transmitting the waveform, they do not contain any energy storing element like a capacitor.
In general, clippers are classified into two types: Series Clippers and Shunt Clippers.
1. Series Clippers
Series clippers are again classified into series negative clippers and series positive clippers which are as
follows:
a. Series Negative Clipper

Series Negative Clipper

The above figure shows a series negative clipper with its output waveforms. During the positive half cycle
the diode (considered as ideal diode) appears in the forward biased and conducts such that the entire

2
Electronic Devices and Instrumentation Lab [18ECL37]
positive half half cycle of input appears across the resistor connected in parallel as output waveform.
During the negative half cycle the diode is in reverse biased. No output appears across the resistor. Thus, it
clips the negative half cycle of the input waveform, and therefore, it is called as a series negative clipper.

Series Negative Clipper With Positive Vr

Series Negative Clipper With Positive Vr

Series negative clipper with positive reference voltage is similar to the series negative clipper, but in this a
positive reference voltage is added in series with the resistor. During the positive half cycle, the diode start
conducting only after its anode voltage value exceeds the cathode voltage value. Since cathode voltage
becomes equal to the reference voltage, the output that appears across the resistor will be as shown in the
above figure.

Series Negative Clipper With Negative Vr

The series negative clipper with a negative reference voltage is similar to the series negative clipper with
positive reference voltage, but instead of positive Vr here a negative Vr is connected in series with the
resistor, which makes the cathode voltage of the diode as negative voltage. Thus during the positive half
cycle, the entire input appears as output across the resistor, and during the negative half cycle, the input
appears as output until the input value will be less than the negative reference voltage, as shown in the
figure.
b. Series Positive Clipper

3
Electronic Devices and Instrumentation Lab [18ECL37]

Series Positive Clipper

The series positive clipper circuit is connected as shown in the figure. During the positive half cycle, diode
becomes reverse biased, and no output is generated across the resistor, and during the negative half cycle,
the diode conducts and the entire input appears as output across the resistor.
Series Positive Clipper with Negative Vr

Series Positive Clipper with Negative Vr

It is similar to the series positive clipper in addition to a negative reference voltage in series with a resistor;
and here, during the positive half cycle, the output appears across the resistor as a negative reference
voltage. During the negative half cycle, the output is generated after reaching a value greater than the
negative reference voltage,  as shown in the above figure.

Series Positive Clipper with Positive Vr

Instead of negative reference voltage a positive reference voltage is connected to obtain series positive
clipper with a positive reference voltage. During the positive half cycle, the reference voltage appears as an
output across the resistor, and during the negative half cycle, the entire input appears as output across the
resistor.

4
Electronic Devices and Instrumentation Lab [18ECL37]

2. Shunt Clippers
Shunt clippers are classified into two types: shunt negative clippers and shunt positive clippers.
a. Shunt Negative Clipper

Shunt Negative Clipper

Shunt negative clipper is connected as shown in the above figure. During the positive half cycle, the entire
input is the output, and during the negative half cycle, the diode conducts causing no output to be generated
from the input.
Shunt Negative Clipper with Positive Vr

Shunt Negative Clipper with Positive Vr

A series positive reference voltage is added to the diode as shown in the figure. During the positive half
cycle, the input is generated as output, and during the negative half cycle, a positive reference voltage will
be the output voltage as shown above.
Shunt Negative Clipper with Negative Vr

Shunt Negative Clipper with Negative Vr

Instead of positive reference voltage, a negative reference voltage is connected in series with the diode to
form a shunt negative clipper with a negative reference voltage. During the positive half cycle, the entire

5
Electronic Devices and Instrumentation Lab [18ECL37]
input appears as output, and during the negative half cycle, a reference voltage appears as output as shown
in the above figure.
b. Shunt Positive Clipper

Shunt Positive Clipper

During the positive half cycle the diode is in conduction mode and no output is generated; and during the
negative half cycle; entire input appears as output as the diode is in reverse bias as shown in the above
figure.

Shunt Positive Clipper with Negative Vr

Shunt Positive Clipper with Negative Vr

During the positive half cycle, the negative reference voltage connected in series with the diode appears as
output; and during the negative half cycle, the diode conducts until the input voltage value becomes greater
than the negative reference voltage and output will be generated as shown in the figure.
Shunt Positive Clipper with Positive Vr

Shunt Positive Clipper with Positive Vr

6
Electronic Devices and Instrumentation Lab [18ECL37]
During the positive half cycle the diode conducts causing the positive reference voltage appear as output
voltage; and, during the negative half cycle, the entire input is generated as the output as the diode is in
reverse biased.
In addition to the positive and negative clippers, there is a combined clipper which is used for clipping both
the positive and negative half cycles as discussed below.
Positive-Negative Clipper with Reference Voltage Vr

Positive-Negative Clipper with Reference Voltage Vr

The circuit is connected as shown in the figure with a reference voltage Vr, diodes D1 & D2. During the
positive half cycle, the diode the diode D1 conducts causing the reference voltage connected in series with
D1 to appear across the output.
During the negative cycle, the diode D2 conducts causing the negative reference voltage connected across
the D2 appear as output, as shown in the above figure.

Working of Clamper Circuit

The positive or negative peak of a signal can be positioned at the desired level by using the clamping
circuits. As we can shift the levels of peaks of the signal by using a clamper, hence, it is also called as level
shifter.
The clamper circuit consists of a capacitor and diode connected in parallel across the load. The clamper
circuit depends on the change in the time constant of the capacitor. The capacitor must be chosen such that,
during the conduction of the diode, the capacitor must be sufficient to charge quickly and during the
nonconducting period of diode, the capacitor should not discharge drastically. The clampers are classified
as positive and negative clampers based on the clamping method.

7
Electronic Devices and Instrumentation Lab [18ECL37]

1. Negative Clamper

Negative Clamper
During the positive half cycle, the input diode is in forward bias- and as the diode conducts-capacitor gets
charged (up to peak value of input supply). During the negative half cycle, reverse does not conduct and
the output voltage become equal to the sum of the input voltage and the voltage stored across the capacitor.

Negative Clamper with Positive Vr

Negative Clamper with Positive Vr

It is similar to the negative clamper, but the output waveform is shifted towards the positive direction by a
positive reference voltage. As the positive reference voltage is connected in series with the diode, during
the positive half cycle, even though the diode conducts, the output voltage becomes equal to the reference
voltage; hence, the output is clamped towards the positive direction as shown in the above figure.

Negative Clamper with Negative Vr

Negative Clamper with Negative Vr

8
Electronic Devices and Instrumentation Lab [18ECL37]
By inverting the reference voltage directions, the negative reference voltage is connected in series with the
diode as shown in the above figure. During the positive half cycle, the diode starts conduction before zero,
as the cathode has a negative reference voltage, which is less than that of zero and the anode voltage, and
thus, the waveform is clamped towards the negative direction by the reference voltage value.

2. Positive Clamper

Positive Clamper
It is almost similar to the negative clamper circuit, but the diode is connected in the opposite direction.
During the positive half cycle, the voltage across the output terminals becomes equal to the sum of the
input voltage and capacitor voltage (considering the capacitor as initially fully charged). During the
negative half cycle of the input, the diode starts conducting and charges the capacitor rapidly to its peak
input value. Thus the waveforms are clamped towards the positive direction as shown above.

Positive Clamper with Positive Vr

Positive Clamper with Positive Vr

A positive reference voltage is added in series with the diode of the positive clamper as shown in the
circuit.
During the positive half cycle of the input, the diode conducts as initially the supply voltage is less than the
anode positive reference voltage. If once the cathode voltage is greater than anode voltage then the diode
stops conduction. During the negative half cycle, the diode conducts and charges the capacitor. The output
is generated as shown in the figure.

Positive Clamper with Negative Vr

9
Electronic Devices and Instrumentation Lab [18ECL37]

Positive Clamper with Negative Vr

The direction of the reference voltage is reversed, which is connected in series with the diode making it as
a negative reference voltage. During the positive half cycle the diode will be non conducting, such that the
output is equal to capacitor voltage and input voltage. During the negative half cycle, the diode starts
conduction only after the cathode voltage value becomes less than the anode voltage. Thus, the output
waveforms are generated as shown in the above figure.

Applications of Clippers and Clampers

Clippers find several applications, such as 
 They are frequently used for the separation of synchronizing signals from the composite picture
signals.
 The excessive noise spikes above a certain level can be limited or clipped in FM transmitters by
using the series clippers.
 For the generation of new waveforms or shaping the existing waveform, clippers  are used.
 The typical application of diode clipper is for the protection of transistor from transients, as a
freewheeling diode connected in parallel across the inductive load.
 Frequently used half wave rectifier in power supply kits is a typical example of a  clipper. It clips
either positive or negative half wave of the input.
 Clippers can be used as voltage limiters and amplitude selectors.

Clampers can be used in applications

 The complex transmitter and receiver circuitry of television clamper is used as a base line
stabilizer to define sections of the luminance signals to preset levels.
 Clampers are also called as direct current restorers as they clamp the wave forms to a fixed DC
potential.
 These are frequently used in test equipment, sonar and radar systems.
 For the protection of the amplifiers from large errant signals clampers are used.
 Clampers can be used for removing the distortions
 For improving the overdrive recovery time clampers are used.
 Clampers can be used as voltage doublers or voltage multipliers.

Procedure:-

1. Set up the circuit on the bread board.

2. Switch on the signal generator and set voltage 10V P-P and frequency 1 KHz.
3. Using CRO measure the output wave form and sees that it matches with required wave form.
4. Repeat this for other clipper and clamper circuits. Result: - All types of clipper and clamper circuits
are tested and output wave form matches with the expected waveform.

10
Electronic Devices and Instrumentation Lab [18ECL37]

Experiment no. : 02
Half wave rectifier and Full wave rectifier
AIM: Half wave rectifier and Full wave rectifier with and without filter and measure the Efficiency and
ripple factor.

Components and equipments required: Center tapped transformer 12 – 0 – 12. IN4007 diodes,
Resistors – 100 Ω - 2nos, DRB, Multimeter, CRO and Bread board.

Half Wave Rectifier without capacitor filter

Half Wave Rectifier with capacitor filter

11
Electronic Devices and Instrumentation Lab [18ECL37]

Full Wave Rectifier:

Full wave Center tapped Without filter Full wave Center tapped With filter

12
Electronic Devices and Instrumentation Lab [18ECL37]

Full wave Bridge Rectifier

13
Electronic Devices and Instrumentation Lab [18ECL37]

Procedure:
Make the Connections as shown in the circuit diagram
 Apply 230V AC supply from the power mains to the primary of the transformer
 Observe the voltage across secondary to get Vm , the peak value in CRO
 Use relevant formula to find Vdc and Vrms of both Full wave and Half wave rectifier & draw the
waveforms
 Find out the Ripple factor, Regulation and Efficiency by using the formula
.

Experiment no. : 03
Zener Diode characteristics and Voltage Regulation

AIM: Characteristics of Zener diode and design a Simple Zener voltage regulator determine line and load
regulation.
Components and equipments required: Zener diode 6.3V or 12V, Power Supply [0-30)V, Milliammeter
(0-10) mA, Voltmeter (0-30)V, DRB, Resistance 1KΩ

Characteristics of Zener diode

Forward Bias Reverse Bias

14
Electronic Devices and Instrumentation Lab [18ECL37]

Zener as Voltage Regulator

15
Electronic Devices and Instrumentation Lab [18ECL37]

Procedure:

Experiment No. 04

LDR and Photo diode and turn on an LED using LDR

AIM: a) Characteristics of LDR and Photo diode,
b) To turn on an LED using LDR
Components and equipments required: LDR, Resistor 1K Ω 330Ω, Power Supply (0-30)V,
Milliammeter (0-10)mA, Transistor BC 547, 100 K POT

a) Characteristics of LDR and Photo diode,

16
Electronic Devices and Instrumentation Lab [18ECL37]

b) To turn on an LED using LDR

Working :
When it’s dark, the LDR has high resistance. This makes the voltage at the base of the transistor too low to
turn the transistor ON. Therefore, no current will go from the collector to the emitter of the transistor. All
the current will instead pass through the LDR and the potentiometer.
When it’s light, the LDR has low resistance. This makes the voltage at the base of the transistor higher.
High enough to turn the transistor ON.
Because the transistor is turned on, current flows through the transistor. It flows from the positive battery
terminal, through R1, the LED, and the transistor down to the negative battery terminal. This makes the
LED light up.
The resistor R1 controls the amount of current going through the LED. It’s simple to calculate. I have
written an article on how to calculate the resistor value for an LED.
If you are using an LED with 2V voltage drop, you will have a 7V voltage drop over the resistor when the
transistor is ON. By using Ohm’s law we can find the current:

17
Electronic Devices and Instrumentation Lab [18ECL37]

And 18 mA is usually a good current value for common LEDs.

Note:
What if you want to power the circuit with something other than a 9V battery? Then you need to change
the resistor value to get the right amount of current flowing through the LED.
The variable resistor R2 is used to change the trigger point for the LED. That is, how much light that is
needed for the LED to turn ON and OFF.

Experiment No. : 05
Static characteristics of SCR
AIM: To plot the characteristics of an SCR and to find the forward resistance, holding current and latching
current.
Components and equipments required: SCR TYN604, Voltmeter (0-30) V, RPS (0-30)V,Milliammeter
(0-30)mA , Resistor 1KΩ/1W, 100 Ω/30W

18
 Electronic Devices and Instrumentation Lab [18ECL37]

I. V – I Characteristics:
i. Make the connections as given in the circuit diagram including meters.
ii. Now switch ON the mains supply to the unit and initially keep V1 &V2 at minimum.
iii. Set load potentiometer RL in the minimum position.
iv. Adjust IG –IG1 say 10 mA by varying VG or gate current potentiometer Rg.
v. Set load potentiometer Rg in the minimum position. Adjust IG –IG1 say 10 mA by varying VG or gate current
potentiometer RG. Slowly vary VL and note down V AK and IA readings for every 5 Volts and entered the
readings in the tabular column.
vi. Further vary VL till SCR conducts, this can be noticed by sudden drop of VAK and rise of IA readings.
vii. Note down this readings and tabulated. Vary VL Further and note down IA and VAK readings. Draw the graph of
VAK V/s IA.
viii. The forward resistance or on state resistance can be calculated from the graph by using formula
Ron-State = ΔVAK/ΔIA Ω.

II. To find latching current:

i. Apply about 20 V between Anode and Cathode by varying VA. Keep the load potentiometer RL at
minimum position. The device must be in the OFF state with gate open.
ii. Gradually increase Gate voltage - Vg till the device turns ON. This is the minimum gate current ( Ig min)
required to turn ON the device.

19
 Electronic Devices and Instrumentation Lab [18ECL37]
iii. Adjust the gate voltage to a slightly higher. Set the load potentiometer at the maximum resistance
position. The device should comes to OFF state, otherwise decrease VA till the device comes to OFF
state.
iv. The gate voltage should be kept constant in this experiment. By varying RL, gradually increase load
current IA in steps. Open and close the Gate voltage VG switch after each step.
v. If the anode current is greater the latching current of the device, the device stays on even after the gate
switch is opened. Otherwise the device goes into blocking mode as soon as the gate switch is opened.
vi. Note the latching current. Obtain the more accurate value of the latching current by taking small steps of
IA near the latching current value.

III. To find Holding current:

i. Increase the load current from the latching current level by load pot RL or VL.
ii. Open the gate switch permanently. The Thyristor must be fully ON.
iii. Now start reducing the load current gradually by adjusting RL.
iv. If the SCR does not turns OFF even after the RL at maximum position, then reduce VL. Observe when
the device goes to Blocking mode.
v. The load current through the device at this instant, is the holding current of the device. Repeat the steps
again to accurately get the IH. Normally IH < IL .

Experiment No. : 06
SCR Controlled HWR and FWR using RC triggering circuit
AIM: RC Half and Full wave firing circuit

20
 Electronic Devices and Instrumentation Lab [18ECL37]
Components and equipments required: SCR TYN604, Voltmeter (0-30) V, RPS (0-30)V,Milliammeter
(0-30)mA , Resistor 1KΩ/1W, 100 Ω/30W,Diode IN4001

a). RC Half wave firing circuits

PROCEDURE:
i. Make the connections as given in the circuit diagram.
ii. Connect a Resistance of 50 ohms between the load points.

21
 Electronic Devices and Instrumentation Lab [18ECL37]
iii. Vary the control pot(R) and observe the voltage waveforms across load, SCR and at different points of
the circuit.
iv. Note down the output voltage across the Load for different values of firing angle in degree.
v. Calculate the theoretical and practical output voltage.
vi. Draw the graph for input wave form, output waveforms across SCR and Load.

Full Wave RC firing circuits

22
Electronic Devices and Instrumentation Lab [18ECL37]

23
 Electronic Devices and Instrumentation Lab [18ECL37]
PROCEDURE :
i. Make the connections as given in the circuit diagram.
ii. Connect a Rheostat of 100 ohms between the load points.
iii. Vary the pot and observe the voltage waveforms across load, SCR and at different points of the circuit.
iv. Note down the output voltage across the Load for different values of firing angle in degree.
v. Calculate the theoretical and practical output voltage.
vi. Draw the graph for input wave form, output waveforms across SCR and Load.

24
Electronic Devices and Instrumentation Lab [18ECL37]

Experiment No.: 08
Wheatstone’s and Kelvin’s Bridges
AIM: Measurement of Resistance using Wheatstone and Kelvin’s bridge
Components and equipments required: Resistor R1= 1KΩ ,R2 = 1KΩ, R3= 47KΩ Pot, Rx = ?
Galvanometer/ Digital Ammeter , RPS (0-10)V

Wheatstone’s Bridge

A Wheatstone Bridge Circuit in its simplest form consists of a network of four resistance arms forming a
closed circuit, with a dc source of current applied to two opposite junctions and a current detector
connected to the other two junctions, as shown in Fig
Wheatstone Bridge Circuit are extensively used for measuring component values such as R, L and C. Since
the bridge circuit merely compares the value of an unknown component with that of an accurately known
component (a standard), its measurement accuracy can be very high. This is because the readout of this
comparison is based on the null indication at bridge balance, and is essentially independent of the
characteristics of the null detector. The measurement accuracy is therefore directly related to the accuracy
of the bridge component and not to that of the null indicator used.
The basic dc bridge is used for accurate measurement of resistance and is called Wheatstone’s bridge.
Wheatstone’s bridge is the most accurate method available for measuring resistances and is popular for
laboratory use. The circuit diagram of a typical Wheatstone Bridge Circuit is given in Fig. The source of
emf and switch is connected to points A and B, while a sensitive current indicating meter, the galva-
nometer, is connected to points C and D. The galvanometer is a sensitive microammeter, with a zero centre
scale. When there is no current through the meter, the galvanometer pointer rests at 0, i.e. mid scale.
Current in one direction causes the pointer to deflect on one side and current in the opposite direction to the
other side.

25
Electronic Devices and Instrumentation Lab [18ECL37]

When SW1 is closed, current flows and divides into the two arms at point A, i.e. I 1 and I2. The bridge is
balanced when there is no current through the galvanometer, or when the potential difference at points C
and D is equal, i.e. the potential across the galvanometer is zero.
To obtain the bridge balance equation, we have from the Fig.

For the galvanometer current to be zero, the following conditions should be satisfied.

Substituting in Eq. 1

This is the equation for the bridge to be balanced.

In a practical Wheatstone Bridge Circuit, at least one of the resistance is made adjustable, to permit
balancing. When the bridge is balanced, the unknown resistance (normally connected at R 4) may be
determined from the setting of the adjustable resistor, which is called a standard resistor because it is a
precision device having very small tolerance.
Hence

26
Electronic Devices and Instrumentation Lab [18ECL37]

PROCEDURE:
 Consider 2 known resistor, 1 potentiometer and 1 unknown resistor which need to be calculated
 Construct the bridge as shown in the circuit diagram
 Vary the Potentiometer such that Ig = 0
 Remove the potentiometer and measure the value through multimeter or ohm meter
 calculate the unknown as per the formulation given Rx = (R2/R1) *R3

Kelvin Bridge

When the resistance to be measured is of the order of magnitude of bridge contact and lead resistance, a
modified form of Wheatstone’s bridge, the Kelvins Bridge theory is employed.
Kelvins Bridge theory is a modification of Wheatstone’s bridge and is used to measure values of resistance
below 1 Ω. In low resistance measurement, the resistance of the leads connecting the unknown resistance to
the terminal of the bridge circuit may affect the measurement.
Consider the circuit in Fig. 11.10, where R represents the resistance of the connecting leads from R 3 to
Rx (unknown resistance).
The galvanometer can be connected either to point c or to point a. When it is connected to point a, the
resistance Ry, of the connecting lead is added to the unknown resistance Rx, resulting in too high indication
for Rx.
When the connection is made to point c, R 3, is added to the bridge arm R 3 and resulting measurement of
Rx is lower than the actual value, because now the actual value of R 3 is higher than its nominal value by the
resistance Ry.
If the galvanometer is connected to point b, in between points c and a, in such a way that the ratio of the
resistance from c to b and that from a to b equals the ratio of resistances R1 and R2, then

27
Electronic Devices and Instrumentation Lab [18ECL37]

and the usual balance equations for the bridge give the relationship

Therefore

Substituting for Rab and Rcb in Eqn 2

PROCEDURE:
 Construct the modified wheatstone’s bridge as shown in the circuit diagram
 Replace the unknown potentiometer value to the fixed value resistance
 Due to lead resistance of the circuit, Ig may be varied, when of the wheatstone bridge is more sensitive
 Vary the Potentiometer such that Ig = 0
 Remove the potentiometer resistance and measure through multimeter or ohm meter

 Calculate the unknown as per the formulation given Rx = (R2/R1) * R3

28
Electronic Devices and Instrumentation Lab [18ECL37]

PART B
Simulation using EDA software (EDWinXP, PSpice, MultiSim, Proteus, Circuit Lab or any equivalent tool)

Experiment No.: 01

AIM:
Components and equipments required: Resistor R1= 1KΩ ,R2 = 1KΩ, R3= 47KΩ Pot, Rx = ?
Galvanometer/ Digital Ammeter , RPS (0-10)V

29