ELECTRONIC CIRCUITS: DEVICES AND ANALYSIS
LABORATORY MANUAL
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COMMON EMITTER CONFIGURATION CHARACTERISTICS
ACTIVITY No. 3
OBJECTIVE
To study the input and output characteristics of a transistor (Common Emitter configuration)
THEORY OVERVIEW
The configuration in which the emitter is connected between the collector and base is known as
a common emitter configuration. The input circuit is connected between emitter and base, and
the output circuit is taken from the collector and emitter. Thus, the emitter is common to both the
input and the output circuit, and hence the name is the common emitter configuration.
The common emitter arrangement for NPN and PNP transistor is shown in the figure below.
Figure 1 NPN Transistor
Figure 2 PNP Transistor
COMPONENT REQUIRED (MULTISIM):
Transistor-NPN BC 107
Resistors (1K, 100K)
DC Source
Ammeter
Voltmeter
CIRCUIT DIAGRAM:
Figure 3 Common emitter circuit.
OPERATION:
The input is applied between base and emitter, the output is taken between collector and
emitter. Input characteristics are obtained between the input current IB and input voltage VBE
at constant output voltage VCE. This portion of an NPN BJT is just like a p-n junction.
Consequently, the IB and VBE relationship in the common emitter configuration is the same as
the I-V characteristic of a diode. The typical value of VBE for silicon BJT is 0.7 V.
Output characteristics are obtained between the output voltage VCE and output current IC
at constant input current IB. The output I-V characteristic consists of a set of curves, one for
each value of IB. In the common emitter configuration, all the I-V curves start from IC = 0 and
VCE and equal to some threshold value. For a given value of IB, the curve increases steeply until
it reaches a level proportional to IB, at which point it flattens (but not completely).
PROCEDURE:
(a) Input Characteristics:
1. Connect the circuit as shown in the circuit diagram.
2. Keep output voltage VCE = 0V by varying VCC.
3. Varying VBB gradually, note down base current IB and base-emitter voltage VBE.
4. Step size is not fixed because of non-linear curve. Initially vary VBB in steps of 0.1V. Once
the current starts increasing, vary VBB in steps of 0.1V.
5. Repeat above procedure (step 3) for VCE = 2V and 5V.
6. Plot the input characteristics: VBE on X-axis and IB on Y-axis at a constant VCE as a
constant parameter.
VCE = 0V
VBE (volts)
IB (µA)
0.500m
0.050m
1.000m
0.100m
1.500m
0.150m
2.000m
0.200m
2.500m
0.250m
2.999m
0.300m
3.499m
0.350m
3.999m
0.400m
4.499m
0.450m
4.999m
0.500m
5.499m
0.550m
VCE = 2V
VBE (volts)
IB (µA)
9.989u
0.999u
0.020m
1.998u
0.030m
2.997u
0.040m
3.996u
0.050m
4.995u
0.060m
5.993u
0.070m
6.992u
0.080m
7.991u
0.090m
8.990u
0.100m
9.989u
0.110m
0.011m
VCE = 5V
VBE (volts)
IB (µA)
(b) Output Characteristics:
1. Connect the circuit as shown in the circuit diagram.
2. Keep emitter current IB = 20 µA by varying VBB.
3. Varying VCC (1V up to 12V), note down collector current IC and Collector-Emitter Voltage
(VCE). 4. Repeat above procedure (step 3) for IB = 40μA and 60μA.
5. Plot the output characteristics: VCE on X-axis and taking IC on Y-axis taking IB as a
constant parameter.
IB = 20µA
VCE (volts)
IC (µA)
IB = 40µA
VCE (volts)
IC (µA)
IB = 60µA
VCE (volts)
IC (µA)
GRAPH:
Ideal Input Characteristics
Ideal Output Characteristics
CONCLUSION
Note: Give a thoughtful conclusion of the experiment. Do not at any point use statements like
“I really learned a lot…” “This helped me learn…” Each student should include his/her own,
individual conclusion.