ENT 162 – Analog Electronics
Laboratory Module
LABORATORY MODULE
ENT 162
Analog Electronics
Semester 2 (2005/2006)
EXPERIMENT 3 : Common-Collector and Common-Base
Amplifiers
Name
:____________________________________________________
Matrix No.
:______________________
PUSAT PENGAJIAN KEJURUTERAAN MEKATRONIK
KOLEJ UNIVERSITI KEJURUTERAAN UTARA MALAYSIA (KUKUM)
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ENT 162 – Analog Electronics
Laboratory Module
EXPERIMENT 3
Common-Collector and Common-Base Amplifiers
Part A: The Common–Collector Amplifier (Emitter–Follower)
1. OBJECTIVE:
1.1
To demonstrate the operation and characteristics of the small-signal Common–
Collector Amplifier and to investigate what influences its voltage gain.
2. PARTS AND EQUIPMENT:
2.1
Resistor 1/4W 68Ω
- 1 Pc
2.2
Resistor 1/4W 100kΩ
- 1 Pc
2.3
Resistor 1/4W 1.0kΩ
- 2 Pcs
2.4
Resistor 1/4W 22kΩ
- 1 Pc
2.5
Resistor 1/4W 27kΩ
- 1 Pc
2.6
Capacitor 25V 2.2µF
- 1 Pc
2.7
Capacitor 25V 100µF
- 1 Pc
2.8
2N3904 NPN Silicon Transistor
- 1 Pc
2.9
0 – 15V DC Power Supply
- 1 Unit
2.10 Signal Generator
- 1 Unit
2.11 Dual Trace Oscilloscope
- 1 Unit
2.12 Breadboard Socket
- 1 Unit
2.13 Multimeter
- 1 Unit
2.14 Jumper Wire
3. INTRODUCTION:
The Common–Collector Amplifier often referred to as an Emitter–Follower, is characterized
by application of the Amplifier input signal to the Base lead while its output is taken from the
Emitter lead. The output signal is never larger than the input but is always in-phase with the
input. The output follows the input. The main advantage is that the input impedance of a
Common–Collector Amplifier is generally much higher than for other bipolar transistor
circuits.
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ENT 162 – Analog Electronics
Laboratory Module
Useful formulas:
1. AV =
Vout
Vin
- Voltage gain from Base to Emitter
2. AV =
R E llR L
( RE + RL ) + r' e
- Voltage gain from Base to Emitter
3. r’e =
25mV
IE
- AC Emitter resistance
4. VB = [
R2
] VCC
R1 + R2
- DC Base voltage
5. VE = VB – VBE
6. IE =
- DC Emitter voltage
VE
RE
- DC Emitter current
7. Rin = R1 ll R2 ll ßac [ ( RE ll RL ) + r’e ]
- Amplifier input impedance
4. PROCEDURE:
4.1
Wire the circuit shown in Figure 3.1. Do not connect the Signal Generator and the
Power Supply yet.
Figure 3.1: Experiment Setup
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ENT 162 – Analog Electronics
4.2
Laboratory Module
Check all connections. Apply the 15 V supply voltage to the breadboard. With a
multimeter, measure the transistor dc Base and Emitter voltage with respect to
Ground. Record your results in Table 3.1. Determine the expected values of these two
voltages (Equation 4 and 5), assuming a Base–Emitter voltage drop of 0.7V and
compare them with the measured values in Table 3.1.
4.3
Connect Channel 1 of your Oscilloscope at point I, Vin and Channel 2 to point O, Vout.
Connect the Signal Generator to the circuit as shown. Adjust the sine wave output
level of the Generator at 0.5V peak-to-peak at a frequency of 5 kHz.
4.4
Using the measured value for the dc Emitter voltage obtained in Step 4.2. Calculate
the dc Emitter current, IE and the resultant transistor ac Emitter Resistance r’e
(Equation 3). Record these values in Table 3.2.
4.5
Using the Oscilloscope, measure the ac peak-to-peak voltage across the 1kΩ load
resistor. Calculate the expected voltage gain from Base to Emitter using Equation 2.
Record this result in Table 3.3. Measure the actual voltage gain by dividing the peakto-peak output voltage, Vout by the peak-to-peak input voltage, Vin. Record your result
in Table 3.3.
4.6
Repeat Step 4.5 using the remaining load resistance values specified in Table.3.3.
Determine the voltage gain by measuring Vout and Vin. Compare your measured result
with the expected value (Equation 3). Record your results in Table 3.3.
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ENT 162 – Analog Electronics
Laboratory Module
Name
:
______________________________
Matrix No
:
______________________________
Date : ______________
5. RESULTS FOR EXPERIMENT 3(A): THE COMMON–COLLECTOR AMPLIFIER
Table 3.1: DC Values
Parameter
VB
VE
Measured Value
Expected Value
% Error
Table 3.2: AC Emitter Resistance
Parameter
IE ( Expected )
r’e ( Expected )
Value
Table 3.3: Amplifier Gain
Load
Resistance
1kΩ
100kΩ
68kΩ
Vin
Vout
Measured
Gain
Expected
Gain
%
Error
6. CALCULATIONS
Instructor Approval :
____________________
Page 5 of 12
Date :
_____________
ENT 162 – Analog Electronics
Laboratory Module
Name
:
______________________________
Matrix No
:
______________________________
Date : ______________
7. QUESTIONS FOR EXPERIMENT 3(A):
1. What is the voltage gain of a Common–Collector Amplifier or an Emitter–Follower?
…………………………………………………………………………………………
2. If the load resistor RL in the circuit is increased, the voltage gain will
…………………………………………………………………………………………
3. Write down 3 characteristics of a Common–Collector Amplifier?
a. …………………………………………………………………………………
b. …………………………………………………………………………………
c. …………………………………………………………………………………
Instructor Approval :
____________________
Page 6 of 12
Date :
_____________
ENT 162 – Analog Electronics
Laboratory Module
Part B: The Common–Base Amplifier
1. OBJECTIVE:
1.1
To demonstrate the operation and characteristics of the Common–Base Amplifier.
1.2
To investigate what influences its voltage gain.
2. PARTS AND EQUIPMENT:
2.1
Resistor 1/4W 470 Ω
- 1 Pc
2.2
Resistor 1/4W 1 kΩ
- 2 Pcs
2.3
Resistor 1/4W 10 kΩ
- 1 Pc
2.4
Capacitor 25V 2.2 µF
- 1 Pc
2.5
Capacitor 25V 100 µF
- 1 Pc
2.6
2N3904 NPN Silicon Transistor
- 1 Pc
2.7
0 – 15V DC Power Supply
- 2 Units
2.8
Signal Generator
- 1 Unit
2.9
Dual Trace Oscilloscope
- 1 Unit
2.10 Breadboard
- 1 Unit
2.11 Multimeter
- 1 Unit
2.12 Jumper Wire
3. INTRODUCTION:
The Common–Base Amplifier is characterized by application of the Amplifier input signals to
the Emitter lead, while its output is taken from the Collector. Same as in the Emitter–
Follower, both signals are in-phase. The voltage gain of the Common–Base Amplifier is like
that of a Common–Emitter Amplifier.
Useful formulas:
1. AV =
Vout
Vin
- Voltage gain from Emitter to Collector
2. AV =
RC llR L
r' e
- Normal circuit with load
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ENT 162 – Analog Electronics
Laboratory Module
3. AV =
RC
RC
r' e
- Without load
4. r’e =
25mV
IE
- Transistor ac Emitter Resistance
5. VE = – VBE
6. IE =
V EE − V BE
RE
7. VC = VCC – ICRC
- Dc Emitter voltage
- Dc Emitter current
- Dc Collector voltage
4. PROCEDURE:
4.1
Wire the circuit shown in Figure 3.2. Do not connect the Signal Generator and the
Power Supply yet.
Figure 3.2: Experiment Setup
4.2
Check all connection. Apply the + 9 V and – 9 V supply voltage to breadboard. With a
multimeter, individually measure the transistor dc Emitter and Collector voltages with
respect to Ground. Record your results in Table 3.4. Based on the resistor values of
Figure 3.2, determine the expected values of these two voltages (Equation 5 and 7),
assuming a Base–Emitter voltage drop of 0.7V and compare them with the measured
values in Table 3.4.
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ENT 162 – Analog Electronics
4.3
Laboratory Module
Using the measured value for the dc Emitter voltage obtained in Step 4.2. Calculate
the dc quiescent Emitter current (Equation 6) and the resultant transistor ac Emitter
Resistance, r’e (Equation 4). Record these values in Table 3.5.
4.4
Connect Channel 1 of your Oscilloscope to point I (Vin) and Channel 2 to point O (Vout).
Then connect the Signal Generator to the circuit as shown in Figure 3.2 and adjust the
sine wave output level of the Generator at 25 mV peak-to-peak at a frequency of 5
kHz.
4.5
Calculate the expected voltage gain from Emitter to Collector using Equation 2. Record
this value in Table 3.6. Measure the actual voltage gain by dividing the peak-to-peak
output voltage, Vout by the peak-to-peak input voltage, Vin (Equation). Record your
result in Table 3.6.
4.6
Remove RL. As in Step 4.5, determine the voltage gain by measuring Vout and Vin.
Compare your measured result with the expected value (Equation 3). Record your
results in Table 3.6.
4.7
Connect a 470 Ω resistor for RL. Calculate the voltage gain from Emitter to Collector
using Equation 2. Record this value in Table 3.6. Measure the actual voltage gain by
dividing the peak-to-peak output voltage, Vout by the peak-to-peak input voltage, Vin
(Equation 3). Record your result in Table 3.6.
Page 9 of 12
ENT 162 – Analog Electronics
Laboratory Module
Name
:
______________________________
Matrix No
:
______________________________
Date : ______________
5. RESULTS FOR EXPERIMENT 3(B): THE COMMON–BASE AMPLIFIER
Table 3.4: DC Values
Parameter
VE
VC
Measured Value
Expected Value
% Error
Table 3.5: AC Emitter Resistance
Parameter
IE ( Expected )
r’e ( Expected )
Value
Table 3.6: Amplifier Gain
Load
Resistance
1 kΩ
None
470 Ω
Vin
Vout
Measured
Gain
Expected
Gain
%
Error
6. CALCULATIONS:
Instructor Approval :
____________________
Page 10 of 12
Date :
_____________
ENT 162 – Analog Electronics
Laboratory Module
Name
:
______________________________
Matrix No
:
______________________________
Date : ______________
7. QUESTIONS FOR EXPERIMENT 3(B):
1.
If the Emitter supply voltage is made more negative, the voltage gain will
…………………………………………………………………………………………
2.
For the circuit in Figure 4.1, VE is approximately
…………………………………………………………………………………………
3.
Write down 3 characteristics of a Common–Base Amplifier:
a)
b)
c)
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
Instructor Approval :
____________________
Page 11 of 12
Date :
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ENT 162 – Analog Electronics
Laboratory Module
Name
:
______________________________
Matrix No
:
______________________________
Date : ______________
8. DISCUSSION:
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9. CONCLUSION:
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