13-08-2013, 03:17 PM
COMMON EMITTER CONFIGURATION
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Objective:
To study the input and output characteristics of a transistor
in common emitter configuration.
Theory
The basic circuit diagram for studying input and output characteristics are shown in fig (1) & fig (2). In this the input is applied between base and emitter and the output is taken from collector and emitter. Here emitter is common to both input and output and hence the name common emitter configuration.
Input characteristics are obtained between the input current and input voltage taking output voltage as parameter. It is plotted between VBE and IB at constant VCE in CE configuration.
Output characteristics are obtained between the output voltage and output current taking input current as parameter. It is plotted between VCE and IC at constant IB in CE configuration.
Procedure
Input Characteristics
1. Make the connections as per circuit diagram fig (1).
2. Keep output voltage VCE = 0V by varying VCC.
3. Varying VBB gradually, note down both base current IB and base - emitter voltage (VBE).
4. Step Size is not fixed because of non linear curve and vary the X-axis variable (i.e if output variation is more, decrease input step size and vice versa).
5. Repeat above procedure (step 3) for VCE =5V.
Output Characteristics
1. Make the connections as per circuit diagram fig (2).
2. By varying VBB keep the base current I B = 20A.
3. Varying VCC gradually, note down the readings of collector-current (IC) and collector-emitter voltage (VCE).
4. Step Size is not fixed because of non linear curve and vary the X-axis variable (i.e if output variation is more, decrease input step size and vice versa).
5. Repeat above procedure (step 3) for IE=40A.
Precautions:
1. While doing the experiment do not exceed the ratings of the
transistor. This may lead to damage the transistor.
2. Connect voltmeter and Ammeter in correct polarities as shown in the
circuit diagram.
3. Do not switch ON the power supply unless you have checked the
circuit connections as per the circuit diagram.
4. Make sure while selecting the emitter, base and collector terminals of
the transistor.