3111- EES- Lab Manual National Textile University
Name
Reg. #
Marks
Experiment 9:
Use Transistor as an amplifier in Proteus Professional
A bipolar junction transistor acts as an amplifier by raising the strength of a weak signal. The DC
bias voltage applied to the emitter base junction, makes it remain in forward biased condition. This
forward bias is maintained regardless of the polarity of the signal. The BJT can be connected in
three amplifier configurations i.e the common-emitter, the common-base, and the common-
collector.
Common Emitter Amplifier
The common-emitter (CE) configuration has the emitter as the common terminal, or ground, to an
ac signal. CE amplifiers exhibit high voltage gain and high current gain.
Procedure:
1. Connect the circuit in Proteus as shown in Figure 19.
Figure 19 Common-emitter Amplifier
2. Using a signal generator, set input voltage Vin such that output voltage Vout is 3V (p-p),
keeping the frequency at 50Hz.
3. Observe the base voltage VS and Vout on the oscilloscope by using both the channels.
Measure and record the reading of Vs, Vout and voltage gain Av in Table 16.
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3111- EES- Lab Manual National Textile University
V P
P
A
V P
P
4. Given that re is 78. Calculate and record the voltage gain Av using:
R
A
r
5. Change R3 (collector resistance) to 1k, 2k, 3k, and record your readings in Table 15.
Table 15 Common-emitter amplifier readings
Vin/mV Collector Measured Measured Measured Calculated
Resistance R3/ Vs (p-p) /V Vout (p-p) /V Av Av
Ω
100 4.7k
100 1k
100 2k
100 3k
Common-Collector Amplifier
The common collector amplifier usually referred as emitter follower (EF). Input is applied at the
base there is coupling capacitor, and the output is at emitter.
Procedure:
1. Connect the circuit in Proteus as shown in Figure 20.
Figure 20 Common-collector amplifier
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3111- EES- Lab Manual National Textile University
2. Using a signal generator, set input voltage Vin so that Vout is 0.1 V (p-p) undistorted sine
wave, keeping the frequency at 50 Hz.
3. Observe the base voltage VS and Vout on the oscilloscope by using both the channels.
Measure and record the reading of Vs, Vout and voltage gain Av in Table 16.
V P
P
A
V P
P
4. Change R4 (emitter resistance) to 1k, 2k, 3k, and record your readings in Table 16.
Table 16 Common-collector amplifier readings
Vin/mV Emitter Measured Measured Measured
Resistance R3/ Vs (p-p) /V Vout (p-p) /V Av
Ω
1k
2k
3k
Common-Base Amplifier
In common-base amplifier, the input ac signal is injected into the emitter-base circuit and output
is taken from the collector-base circuit. The E/B junction is forward-biased by VEE whereas C/B
junction is reverse-biased by VCC.
Procedure:
1. Connect the circuit in Proteus as shown in Figure 21.
Figure 21 Common-base amplifier
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3111- EES- Lab Manual National Textile University
1. Using a signal generator, input voltage Vin to 100mV and keep its frequency at 50Hz.
2. Observe the collector voltage VS and Vout on the oscilloscope by using both the channels.
Measure and record the reading of Vs, Vout and voltage gain Av in Table 17.
V P
P
A
V P
P
3. Given that re is 29. Calculate and record the voltage gain Av using:
R
A
r
4. Change R3 (collector resistance) to 1k, 2k, 3k, and record your readings in Table 17.
Table 17 Common-base amplifier readings
Vin/mV Collector Measured Measured Measured Calculated
Resistance R3/ Vs (p-p) /V Vout (p-p) /V Av Av
Ω
100 4.7k
100 1k
100 2k
100 3k
Questions
1. Can the same voltage gain be achieved with a common base as with a common emitter
amplifier?
2. Which configuration has the highest voltage gain and why?
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