Isra University
Practical # 02
Subject: Basic Electronics (ESBE-102)
Semester: 2nd (Spring 2013)
Batch: Fall 2012
Student’s Name:
ID: 1210-BE (EE)-
Department: Electrical Engineering
Date: 20-08-2013
Grade & Sig:
Title: Voltage-Current characteristics of forward biased diode.
Objective: Objective of this practical is to learn that how a diode can be made forward biased
and what are the values of voltage across and current through forward biased diode.
Required Apparatus:- Few diodes, breadboard, multimeter, 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 is said to be forward biased; if positive terminal of diode is connected with positive of
voltage source and negative terminal of diode is connected with negative of voltage source.
Silicon diode will conduct current at 0.7volt and germanium diode will conduct current at
0.3volt when forward biased. 0.7volt is also called barrier potential for silicon diode and
0.3volt is barrier potential for germanium diode. Before the value of voltage across diode
reaches its barrier potential; there is very small amount of current that is flowing through
diode. After the value of voltage across diode reached its barrier potential; there is a rapid
change in the value of current through diode. This phenomenon is shown in figure 01.
Figure 01: Current Voltage characteristic curve for forward biased diode
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Department of Electrical Engineering & Computer Science
ISRA UNIVERSITY HYDERABAD
Procedure:- Connect positive terminal of a diode with positive of battery and connect
negative terminal of a diode with negative of battery as shown in figure 02; a current limiting
resistor may also be added in series with diode.
Figure 02: Forward biased diode
Observation:- When value of forward voltage across diode is less than its barrier potential;
the value of forward current is very small. As soon as value of forward voltage across diode
is reached to its barrier potential; there is rapid increase in forward current.
Answer the following questions:Question 01: What is the value of barrier potential for silicon diode?
Question 02: What is the value of barrier potential for germanium diode?
Question 03: How to make a diode forward biased with the help of battery (voltage source)?
Question 04: What is barrier potential?
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Department of Electrical Engineering & Computer Science
ISRA UNIVERSITY HYDERABAD
Question 05: Draw current voltage characteristic curve for forward biased silicon diode.
Question 06: Draw current voltage characteristic curve for forward biased germanium diode.
Question 07: Fill in the following table.
VF
0.1v
0.2v
0.3v
0.4v
0.5v
0.6v
0.7v
0.8v
0.9v
IF for silicon diode
IF for Germanium diode
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Department of Electrical Engineering & Computer Science
ISRA UNIVERSITY HYDERABAD