Isra University
Practical # 07
Subject: Basic Electronics (ESBE-102)
Department: Electrical Engineering
Semester: 2nd (Spring 2013)
Batch: Fall 2012
Date:
Student’s Name: ________________ ID: 1210-BE (EE)-_____ Grade & Sig:____________
Title: Diode Clipper Circuit.
Objective: Objective of this practical is to learn that how a diode can clip/limit the signal.
Required Apparatus:- Few diodes, breadboard, multimeter, Oscilloscope, step down
transformer, connecting wire etc.
Theory:- Diode is a two terminal semiconductor device with an ability to conduct current
only in one direction after a certain amount of voltage called barrier potential is applied to it
in a proper way. Diode is one of great invention which is used in many applications such as
rectifier circuits, voltage limiter circuits, voltage clamper circuits, voltage multiplier circuits
etc.
Diode limiter circuits are usually used to limit the +ve and/or –ve input signal. Positive diode
limiter circuit is shown in figure 01(a) and negative diode limiter circuit is shown in figure
01(b). When positive input half cycle of voltage signal is applied to circuit as shown in figure
01(a); diode will be forward biased and it can drop only 0.7volt and remaining input voltage
will be dropped across R1. When negative input half cycle of voltage signal is applied to
circuit as shown in figure 01(a); diode will be reverse biased and it will appear as open
switch, so input voltage will be dropped across series combination of R1 and RL.
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ISRA UNIVERSITY HYDERABAD
When negative input half cycle of voltage signal is applied to circuit as shown in figure
01(b); diode will be forward biased and it can drop only 0.7volt and remaining input voltage
will be dropped across R1. When positive input half cycle of voltage signal is applied to
circuit as shown in figure 01(b); diode will be reverse biased and it will appear as open
switch, so input voltage will be dropped across series combination of R1 and RL.
Figure 01: Diode limiter circuit. (a) Positive limiter (b) Negative limiter
Input and output signal waveforms are also shown in figure 01.
Procedure:- Prepare the circuit on bread board as given in figure 01. Observe the input and
output signal waveforms on oscilloscope.
Observation:- Input and output signal waveforms resemble with the waveforms as given in
figure 01.
Answer the following questions:Question 01: What is diode clipper circuit?
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Question 02: What is difference between positive and negative diode clipper circuit?
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Question 03: What is biased clipper circuit?
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Question 04: What is difference between positive biased and negative biased clipper circuit?
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Question 05: Draw circuit diagram for; (i) Positive diode clipper circuit (ii) Negative diode
clipper circuit (iii) Positive biased diode clipper circuit (iv) Negative biased diode clipper
circuit.
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Department of Electrical Engineering & Computer Science
ISRA UNIVERSITY HYDERABAD
Isra University
Practical # 08
Subject: Basic Electronics (ESBE-102)
Department: Electrical Engineering
Semester: 2nd (Spring 2013)
Batch: Fall 2012
Date:
Student’s Name: ________________ ID: 1210-BE (EE)-_____ Grade & Sig:____________
Title: Diode Clamper Circuit.
Objective: Objective of this practical is to learn that how a diode can clamp the signal.
Required Apparatus:- Few diodes, breadboard, multimeter, Oscilloscope, step down
transformer, connecting wire etc.
Theory:- Diode is a two terminal semiconductor device with an ability to conduct current
only in one direction after a certain amount of voltage called barrier potential is applied to it
in a proper way. Diode is one of great invention which is used in many applications such as
rectifier circuits, voltage limiter circuits, voltage clamper circuits, voltage multiplier circuits
etc.
Diode clamper circuits also known as DC restorer circuits are usually used to add DC level to
an AC signal. Positive diode clamper circuit is shown in figure 01 and negative diode clamper
circuit is shown in figure 02.
Positive diode clamper circuit inserts a positive DC level in the output waveform. When
negative half cycle of input AC signal is provided to positive diode clamper circuit, diode is
forward biased and capacitor will be charged up to voltage level (Vin-0.7), because diode has
to drop 0.7volts. During when positive half cycle of input AC signal is provided to positive
diode clamper circuit, diode is reverse biased and as capacitor is already charged up to
voltage level (Vin-0.7)volts, now this capacitor will work as a battery of (Vin-0.7)volts, that’s
why capacitor voltage is added with positive half cycle of AC input signal, furthermore this
capacitor voltage will also be added with next negative half cycle of input AC signal. In result
input AC signal is shifted upward by the magnitude of (Vin-0.7)volts.
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Figure 01: Positive diode clamper circuit
Negative diode clamper circuit inserts a negative DC level in the output waveform. When
positive half cycle of input AC signal is provided to negative diode clamper circuit, diode is
forward biased and capacitor will be charged up to voltage level (Vin-0.7), because diode has
to drop 0.7volts. During when negative half cycle of input AC signal is provided to negative
diode clamper circuit, diode is reverse biased and as capacitor is already charged up to
voltage level (Vin-0.7)volts, now this capacitor will work as a battery of (-Vin+0.7)volts,
that’s why capacitor voltage is added with negative half cycle of AC input signal, furthermore
this capacitor voltage will also be added with next positive half cycle of input AC signal. In
result input AC signal is shifted downward by the magnitude of (Vin-0.7)volts.
Figure 02: Negative diode clamper circuit
Input and output signal waveforms are also shown in figure 01 and 02. For good clamping
action, a clamper circuit requires a capacitor with RC time constant at least 10 times the
period of input signal.
Procedure:- Prepare the circuit on bread board as given in figure 01 and/or 02. Observe the
input and output signal waveforms on oscilloscope.
Observation:- Input and output signal waveforms resemble with the waveforms as given in
figure 01 and 02 for positive and negative diode clamper circuit respectively.
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Answer the following questions:Question 01: What is diode clamper circuit?
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Question 02: What is difference between positive and negative diode clamper circuit?
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Question 03: What is biased clamper circuit?
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Question 04: What is difference between positive biased and negative biased clamper circuit?
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Question 05: Draw circuit diagram for; (i) Positive diode clamper circuit (ii) Negative diode
clamper circuit (iii) Positive biased diode clamper circuit (iv) Negative biased diode clamper
circuit.
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Department of Electrical Engineering & Computer Science
ISRA UNIVERSITY HYDERABAD
Isra University
Practical # 09
Subject: Basic Electronics (ESBE-102)
Department: Electrical Engineering
Semester: 2nd (Spring 2013)
Batch: Fall 2012
Date:
Student’s Name: ________________ ID: 1210-BE (EE)-_____ Grade & Sig:____________
Title: Diode voltage multiplier circuit (Specifically diode voltage doubler circuit).
Objective: Objective of this practical is to learn that how a diode voltage multiplier circuit
can raise the amplitude of input AC signal at input to provide pulsating DC signal with higher
amplitude than peak voltage of AC input signal
Required Apparatus:- Few diodes, breadboard, multimeter, Oscilloscope, step down
transformer, connecting wire etc.
Theory:- Diode is a two terminal semiconductor device with an ability to conduct current
only in one direction after a certain amount of voltage called barrier potential is applied to it
in a proper way. Diode is one of great invention which is used in many applications such as
rectifier circuits, voltage limiter circuits, voltage clamper circuits, voltage multiplier circuits
etc.
Diode voltage multiplier circuits increase the amplitude of input signal “n” times, where
n=2,3,4 are common multipliers. In this practical voltage doubler circuit will be discussed,
implemented and observed. In voltage doubler circuit value of output pulsating DC signal is
almost two times the peak value of input AC signal or simply Voltage doubler is a voltage
multiplier with a multiplication factor of two. Circuit for diode half wave voltage doubler is
shown in shown in figure 01.
Figure 01: Diode half wave voltage doubler
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ISRA UNIVERSITY HYDERABAD
The name “half wave” voltage doubler is taken from the fact that output of half wave voltage
doubler is same as filtered output of half wave rectifier. During positive half cycle of input
AC signal, diode D1 is forward biased, and diode D2 is reverse biased, so capacitor C1 is
charged up to voltage level of (Vp-0.7) volts as shown in figure 01(a). During negative half
cycle of AC input signal diode D2 is forward biased and diode D1 is reverse biased. As
capacitor C1 is already charged, so it will act as a battery source with voltage of -(Vp0.7)volts; which will be added with negative half cycle of input signal. As 0.7 volts will be
dropped across D2; so capacitor C2 will be charged up (2Vp-1.4)volts. If diode forward
biased voltage drops at D1 and D2 are neglected, then C2 will provide pulsating DC voltage
of value equal to 2Vp of input AC signal.
Procedure:- Prepare the circuit on bread board as given in figure 01. Observe the input and
output signal waveforms on oscilloscope.
Observation:- Output voltage is equal to 2Vp.
Answer the following questions:Question 01: What is diode voltage multiplier circuit?
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Question 02: What is difference between diode voltage doubler, tripler and quadrupler
circuit?
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Question 03: Draw shape of output signal for circuit given in figure 01?
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Question 04: Draw circuit diagram and shape of input and output signal for; (i) Half wave
voltage doubler circuit (ii) full wave voltage doubler circuit (iii) Voltage Tripler circuit (iv)
Voltage quadrupler circuit
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Department of Electrical Engineering & Computer Science
ISRA UNIVERSITY HYDERABAD
Isra University
Practical # 10
Subject: Basic Electronics (ESBE-102)
Department: Electrical Engineering
Semester: 2nd (Spring 2013)
Batch: Fall 2012
Date:
Student’s Name: ________________ ID: 1210-BE (EE)-_____ Grade & Sig:____________
Title: Voltage regulation with Zener diode
Objective: Objective of this practical is to learn that how a Zener diode regulates voltage
Required Apparatus:- Few Zener diodes, breadboard, multimeter, Oscilloscope, step down
transformer, connecting wire etc.
Theory:- Zener diode is one of the types of diode which was developed by scientist Zener
Clarence. Zener diode is a heavily doped silicon PN junction device that is designed to
operate in reverse breakdown region. In Zener diode two types of reverse breakdowns occur.
(i) Zener break down (ii) Avalanche breakdown
Zener breakdown: It Occurs at low reverse voltage, Occurs only in Zener diode 
(ii) Avalanche breakdown:
 Occurs at sufficiently high reverse voltage such that diode will be damaged

Occurs in both rectifier and Zener diode 
Due to heavy doping depletion region becomes thin and there are enough charge carriers
(majority and minority) in P & N region, that’s why less voltage is required by Zener diode to
operate in reverse breakdown region. When Zener diode reaches Zener break down voltage
“Vz”, its voltage remains almost constant even though the current changes drastically as
shown in the figure 01. In other words it can also be said that when Zener diode is operating
in Zener breakdown region, it acts as voltage regulator for specified range of reverse current.
Due to characteristic of voltage regulation, Zener diode equivalent circuit is consisting of a
voltage source as shown in figure 02. Zener diode does not produce DC voltage, but constant
voltage drop is represented by a constant DC voltage source.
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Zeners are available with breakdown voltages from 1.8 to 200 volt with tolerance from 1% to
20%
Figure 01: IV characteristic curve for Zener diode
Figure 02: Schematic symbol of Zener diode and it equivalent circuit (a) ideal model
(b) practical model
Procedure:- Prepare a series circuit consisting of a resistor, Zener diode and DC voltage
source as shown in figure 03.
Figure 03: Zener diode as a voltage regulator
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Observation:- When input voltage is sufficiently increased then voltage across Zener diode
remains constant even though current is changing w.r.t to input voltage.
Answer the following questions:Question 01: What is Zener diode?
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Question 02: Describe two types of reverse break downs that can occur in Zener diode.
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Question 03: Draw Zener diode symbol and its equivalent circuit.
Question 04: What is the application of Zener diode in DC power supply?
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Department of Electrical Engineering & Computer Science
ISRA UNIVERSITY HYDERABAD
Isra University
Practical # 11
Subject: Basic Electronics (ESBE-102)
Department: Electrical Engineering
Semester: 2nd (Spring 2013)
Batch: Fall 2012
Date:
Student’s Name: ________________ ID: 1210-BE (EE)-_____ Grade & Sig:____________
Title: Introduction to light emitting diode (LED), its working principle and terminal
identification
Objective: Objective of this practical is learn about LED, how it works and how to identify
its terminals
Required Apparatus:- Few LEDs, breadboard, multimeter, DC power supply, connecting
wire etc.
Theory:- Light emitting diode (LED) falls into category of optical devices/diodes. LED is a
two terminal simple PN junction diode with large exposed area on one layer and it is used to
emit the light when proper forward bias voltage is applied to it. Internal working structure and
schematic symbol of LED is shown in the figure 01(a) and (b) respectively.
(a)
(b)
Figure 01: (a) Internal working structure of LED (b) Schematic symbol of LED
When LED is forward biased, conduction electrons from n-type material cross the pn junction
to combine with conduction holes in p-type material and finally fall into valence band of ptype material by releasing some energy in the form of heat and light. This discrete amount of
light energy is known as photon. This process of light emission in the form of photon is called
electroluminescence. Doping material determines the wavelength of emitted light and
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Wavelength determines the color of light and if it is visible or infrared. Different colors are
obtained by using different combinations of elements
Typical forward voltage drop across LED ranges from 1.2volt to 3.2volt and reverse voltage
drop across LED ranges from 3volt to 10volt. Amount of output light is directly proportional
to amount of current flowing through LED as shown in figure 02. Supplied current for an
LED should be less than maximum current specified in datasheet.
Figure 02: (a) Forward biased LED (b) LED curve for output light versus forward current
Procedure:- Take different LEDs and identify their terminals with the help (i) Ohm meter
(ii) LED casing.
Forward resistance of LED is in the range of kilo ohms and reverse resistance of LED is in
the range of mega ohms/out of range or simply forward resistance of LED should be less than
reverse resistance.
Terminals of LED can be identified with respect to its casing as given in figure 03.
Figure 03: LED terminal identification
Connect LED in forward biased way as shown in figure 02(a) and check voltage drop across
its terminals.
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Observation:-



Terminals of LED are identified


Forward voltage drop across LED terminals is found around 1.2v to 3.2v. 

Light out is directly proportional to current through LED 
Answer the following questions:Question 01: What is an LED?
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Question 02: Describe working procedure of an LED.
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Question 03: What is typical range of forward voltage drop across LEDs?
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Question 04: What is typical range of reverse break down voltage for LEDs?
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Question 05: How to identify terminals of an LED?
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Department of Electrical Engineering & Computer Science
ISRA UNIVERSITY HYDERABAD
Isra University
Practical # 12
Subject: Basic Electronics (ESBE-102)
Department: Electrical Engineering
Semester: 2nd (Spring 2013)
Batch: Fall 2012
Date:
Student’s Name: ________________ ID: 1210-BE (EE)-_____ Grade & Sig:____________
Title: Identification of transistor type and its terminals
Objective: Objective of this practical is to identify transistor type such as (i) NPN (ii) PNP,
and its terminals such as emitter, base and collector.
Required Apparatus:- Few transistors, breadboard, multimeter, connecting wire etc.
Theory:- Transistor is semiconductor device, it is constructed of three doped semiconductor
materials. Either n-type material is sandwiched between two p-type materials or p-type
material is sandwiched between two n-type materials and these three materials make three
regions of transistor as shown in figure 01. Three regions of transistor are known as Base (B),
Collector (C), Emitter (E), these regions separated by two pn-junctions known as base-emitter
and base-collector junction. A wire lead is connected to each of three regions, and these leads
are labeled as E,B,C for emitter, Base, Collector respectively. Emitter is heavily doped, Base
is lightly doped, and Collector is moderately doped. Physically collector is bigger than
emitter and base, because collector has to dissipate more power. Transistors are usually used
as amplifiers and switches. Schematic symbol of transistor is shown in figure 02.
Figure 01: Structure of npn (on left side) and pnp (on right side) transistor
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Figure 02: Schematic symbol of transistor (a) npn (b) pnp
Not only forward resistance of base emitter junction is slightly higher than the resistance of
base collector junction but also forward voltage drop of base emitter junction is slightly
higher than the forward voltage of base collector voltage.
Procedure:- Transistor terminals can be identified with any of following methods:
(i) ohm meter (ii) diode option on digital multimeter (iii) case identification
(i) Transistor terminal identification using ohm meter
In transistor there are two pn-junctions, when ohm meter is connected with any of two leads
and if that junction of transistor is forward biased then it will show some value of resistance
else it will show “OUT of Range”. So find out both junctions with the help of ohm meter,
such that both junctions are forward biased. Now check if common terminal of transistor is
connected with positive probe of ohm meter; transistor is said to be npn else pnp. This
common terminal is base. Junction with slightly higher resistance is base emitter, so emitter
terminal is also identified. Junction with slightly lower resistance is base collector, so
collector terminal is also identified.
RBE>RBC very minor difference (forward resistance is round about in the range of kilo ohms)
(ii) Transistor terminal identification using diode option on digital multimeter
First identify common terminal and type of transistor such as npn or pnp. Then junction with
slightly higher forward voltage drop is base emitter and junction with slightly lower forward
voltage drop is base collector. All three terminals are identified.
VBE>VBC very minor difference (forward voltage drop is round about 0.7 volt)
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(ii) Transistor terminal identification with the help of transistor case
Transistor terminal identification with the help of case is very easy as shown in figure 03. But
care must be taken, because same case may have different terminal configuration by different
manufacturers.
Figure 03: Transistor terminal identification with the help of its case
Observation:Transistor type such as npn or pnp and its terminals are identified.
Answer the following questions:Question 01: What is a transistor?
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Question 02: What are the applications of transistor?
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Question 03: What is the structure of transistor?
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Question 04: Draw schematic symbol for pnp and npn transistor.
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ISRA UNIVERSITY HYDERABAD
Question 05: How to identify transistor terminals?
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Question 06: Mention different readings that you have observed during transistor terminal
identification.
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Department of Electrical Engineering & Computer Science
ISRA UNIVERSITY HYDERABAD