EET120
Semiconductor Devices
Experiment 7: The Common-Collector Amplifier
Objectives:
After completing this experiment, you should be able to,
1. Calculate and measure the DC & AC parameters of the Common-Collector (CC) amplifier.
2. Observe the effect of the by-pass capacitor on amplifier voltage gain.
Components needed:
1. Resistors: (1) 33 k?, 10k?, 100 ?, (2) 1k?
2. Capacitors: 1 µF, 10 µF
3. Transistor: (1) PNP – 2N3906
4. Multisim
Procedure:
1. Build the following circuit in multisim.
VCC 12V
Q1
2N3906
R1
kΩ
33
R2
kΩ
10
RC
100Ω
RE
1
kΩ
Figure 1: DC Equivalent circuit of CC amplifier
2. Calculate the DC parameters listed in Table 2 for the circuit shown in Figure 1.
DC Parameters
Calculated Value
Measured value
VB
2.79V
3.12V
VE
3.49V
3.88V
IE
8.51mA
8.12mA
VC
851mV
807mV
VCE
-2.64V
-3.076V
Table 2: Calculated and measured DC parameters
3. Measure and record the values in Table 2 using the DMM.
4. Modify the circuit as shown in Figure 2.
Q1
2N3906
VCC
V
12
Pin 49
R1
kΩ
33
R2
kΩ
10
RC
100Ω
C1
µF
1
VS
0.5
Vppk
1
kHz
0
°
C3
10
µF
RL1
kΩ
1
RE
1
kΩ
Figure 2: The Common – Collector Amplifier
Input voltage
VIN
Output voltage
VOUT
Voltage gain
AV
500mVPP
494mV
0.988
1VPP
970mV
0.97
2VPP
1.934V
0.967
3VPP
2.9V
0.97
Table 3: Calculated and measured AC parameters
10. Set the AC Source voltage to 500mVPP, 1 kHz sinewave.
11. Connect the first channel of the Oscilloscope across the AC source.
12. Connect the second channel of the Oscilloscope across the 1 k? load resistor.
13. You should be able to observe the signals as shown in Figure 3. Note: your scope screen may look different.
Figure 3: Input and Output signals of the CE Amplifier
14. By observing the input and output signals of the amplifier, the phase difference between them is approximately _____0____ degrees.
15. Record the output voltage Table 3.
16. Calculate the voltage gain (Av) using the measured input and output voltages using the formula below. Record the result in Table 3 under Voltage gain Av.
Voltage gain
17. Repeat step 15 and 16 by changing the input voltage as shown in Table 3 and record the results.
18. Summarize your observations on voltage gain below.
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Example:
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