UNIVERSITY OF BAHRAIN
Department of Electrical and Electronics Engineering
Multi-Stage (Cascaded) Amplifiers
EXPERIMENT 1
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EENG262
EXPERIMENT 1
Multi-Stage (Cascaded) Amplifiers
Objective
Study of the multistage (cascaded) amplifier:
1. To investigate the effect of cascading on the amplifier gain
2. To study the phase relationships between input & output
3. To determine the range of linear operation of the amplifier.
Learning Outcome:
This lab assignment satisfies the Course Learning Outcome #1, which is, Analyse multistage (cascade and
cascode) circuits. Current Sources and current mirrors
Apparatus
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Variable DC Power Supply
Dual Trace Oscilloscope
Digital Multi-meter
2N2222 Transistors
Resistors
22uF Capacitors
Method
This lab has been designed to teach the students how to use the lab equipment to measure and to
manipulate the output of the given circuit.
This document is to be submitted to the tutor by hardcopy next lab period and also by email in the due
time announced.
Marking Scheme
Rubrics
Attendance
Results
Discussion
Conclusion
Layout
Performance
Total
Marks
Assigned
10
40
20
10
10
10
100
Student
Marks
/100
Remark: Attendance is dominating the grade of the laboratory report i.e. not attending means
no need to submit the report.
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Theory and Background
Multistage amplifiers can be used to realize the design specifications, which are impossible to obtain from a single stage
amplifier, e.g., specifications of an Op amp. Two amplifiers are said to operate in cascade when the output signal of the
first stage serves as the input signal to the second. Amplifiers may be coupled using : RC- coupling, direct coupling ,
transformer coupling and impedance coupling. When two amplifiers are cascaded, their overall voltage gain and gainbandwidth product are greater than that of individual stages, but the bandwidth is smaller. In cascaded amplifiers, the
effect of loading of the second stage on the first must be considered.
Circuit Diagram
R1
47KΩ
RS
10KΩ
RC1
4.7KΩ
C1
R3
vo1
47KΩ
22uF
RC2
4.7KΩ
RE1
1KΩ
C3
vo2
22uF
Q1
2N2222
22uF
R2
vin
10mv 10KΩ
C2
Q2
2N2222
R4
CE1
22uF
10kΩ
Vcc
10V
RE2
1KΩ
Figure (1)
Equipment and components:
In this experiment, you will require the following Equipment & Components:
DC power supply, Oscilloscope, digital multimeter, signal generator.
Transistors (2N2222), R & C components.
Q1, Q2 : 2N2222 BJT’s
VCC = 10 V
RC1 = RC2 = 4.7 K Rs = 10 K
R2 = R4 = 10 K RE1 = RE2 = 1 K C1 = C2 = C3 = Cs1 = 22 F
R1 = R3 = 47 K
Procedure
1. Construct the circuit shown in the figure (1).
2. With no signal (vs =0), make measurements of DC voltages at each node.
3. Apply a 1kHz sine-wave signal to the amplifier.
4. Connect an oscilloscope to examine the input output waveforms. Set the signal-level vs (10mv) such that no distortion
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is present at the outputs of the two stages.
5. Plot and record the peak to peak voltages at vin, vo1, and vo2. Also record your observations on phase shifts.
6. Calculate the voltage gains of the first & second stages and the overall gain.
7. Disconnect the jumper wire between the first stage(figure (2)) and second one (figure(3))and read vin and vo( take a
snap shot of vo then calculate Av of each.
8. Compare the overall voltage gain of the cascade amplifier with that resulted from the multiplication of individual
stages voltage gain. Are they equal? If not why?
Observations
DC Measurements
VB1 =
VC1 =
VE1 =
VB2 =
VC2 =
VE2 =
AC Measurements
Cascade [Overall voltage gain]
vin =
vo1 (1st stage Voltage)=
1st Stage alone
vin1 = (as above)
vo1 (1st stage Voltage) =
R1
47KΩ
RS
Av= vo / vin =
vo (Final Voltage)=
Av1= vo1/ vin1 =
RC1
C2
4.7KΩ
vo1
C1
22uF
Vcc
10V
10KΩ
vin
Q1
22uF
R2
10KΩ
RE1
1KΩ
Figure(2)
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CE1
22uF
2nd Stage alone
vin2 = (as above)
vo2 (2nd stage Voltage) =
Av2= vo2/ vin2 =
RC2
R3
47KΩ
C4
4.7KΩ
C3
Avtot =Av1*Av2=
vo2
Vcc
22uF
Q2
10V
22uF
R4
vin2
RE2
10KΩ
1KΩ
Figure(3)
Discussion and Conclusion
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Write a brief report, which should have Objective, Observations, Comment, Calculations and answer to the
.following
Give your comments on the effect of cascading on voltage gain
Give your comments on the phase shifts between input and at vin and v2 & vo.
Comment on the linear range of the circuit.
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Using the DC measurements, find the BJT-parameters.
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Calculate the gains of the first, second stages and the overall circuit, using hybrid- model for the transistors.
Compare with the experimental results.
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Simulate the circuit using CAD tool.
Vo1
Measured
Calculated
Simulated
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Vo2
Av
Av1
Av2
Avtot
Av compared
to Avtot