EXP1 BJT CE AMPLIFIER DC AND AC

Analog Electronic Circuits (EKT 204) Semester 1 2010/2011
Exp. 1
UNIVERSITI MALAYSIA PERLIS
ANALOG ELECTRONIC CIRCUITS
EKT 204/4
EXPERIMENT # 1
BJT COMMON EMITTER AMPLIFIER
DC AND AC OPERATION
MARKS
Pre Lab
IDC
&V
βDC
5
5
1
DC
load
line
3
re
Av
D
C
Total
1
3
4
3
25
NAME
PROGRAMME
MATRIK #
DATE
Analog Electronic Circuits (EKT 204) Semester 1 2010/2011
Exp. 1
EXPERIMENT 1
BJT Common Emitter Amplifier
1.
OBJECTIVE:
1.1
DC OPERATIONAL EFFECTS
The experimental objectives are to:
i) Compare the amplifier theoretical and practical DC operational values, and
in particular the ‘quiescent’ operating point (‘Q’ point).
ii) Determine the effect of coupling capacitors and bypass capacitors on the ‘Q’
point.
iii) Determine the effect of the load on the ‘Q’ point.
iv) Determine the transistor operational βDC and compare with the 2N3904 data
sheet.
v) Draw the DC load line.
1.2
AC OPERATION
The experimental objectives are to:
i) Compare the theoretical and practical amplifier voltage gain.
ii) Determine the effect of the load on the amplifier voltage gain.
iii) Observe the effect of unbypassed emitter resistors.
2.
INTRODUCTION:
In this lab, the common-emitter configuration will be investigated. This common-emitter
amplifier typically uses a self biasing scheme and has a relatively linear output. The common-emitter
amplifier is characterized by high voltage (Av) and current gain (Ai).The amplifier typically has a
relatively high input resistance (1 to 10k ohms) and is generally used to drive medium to high resistance
loads. The circuit for the common-emitter can be seen in Figure 1. It is used in applications where a small
voltage signal needs to be amplified to a large voltage signal. Since the amplifier cannot drive low
resistance loads, it is usually cascaded with a buffer that can acts as a driver.
FIGURE 1: Common Emitter Amplifier.
3.
EQUIPMENT:
2.1
2.2
2.3
2.4
Dual-trace oscilloscope
Function Generator
Voltmeter
Breadboard
Analog Electronic Circuits (EKT 204) Semester 1 2010/2011
4.
Exp. 1
PROCEDURE:
BJT COMMON EMITTER AMPLIFIER:
10.6V
20uAmp
20UAMP
FIGURE 2
PART A: DC OPERATION
i) From FIGURE 2 amplifier circuit, do a pre lab calculation for DC operational conditions:
(Assume βDC=100 VBE(ON)=0.7V)
a) IC
b) VE
c) VCC
d) VCE
e) VB
f) R1
g) re
h) Zin
i) Zout
j) Gain Av (with C2 and without C2)
ii) Construct the amplifier circuit as shown in FIGURE 2.
Analog Electronic Circuits (EKT 204) Semester 1 2010/2011
Exp. 1
iii) Using a multimeter, measure DC currents and DC voltages with C2 and without C2 in the
circuit. Record all the values.
a. DC currents: IB, IC, IE
b. DC voltages: Vcc, VB, VBE, VC, VCE, VE, Vload.
(5 M)
iv) Using IB and IC measurement values, calculate βDC.
(1 M)
v) From the result, clearly indicate the major points and sketch a DC load
line.
(3 M)
PART B: AC OPERATION
10.6V
20UAMP
FIGURE 3
i)
Set both oscilloscope channels to ac coupled.
ii)
Set gnd positions both channels.
iii)
Set the signal generator input (VIN) as shown in FIGURE 3 to 0.1V peak-peak at
1 kHz.
iv)
Reduce the input voltage if the output voltage waveform, CH2, is
clipped
v)
vi)
(1 M)
By using IE measurement, calculate re .
Find Voltage Gain Av (measurement) for amplifier circuit with C2 and without C2.
(3 M)
Analog Electronic Circuits (EKT 204) Semester 1 2010/2011
5.
Exp. 1
DISCUSSION:
i) In the DC equivalent circuit of an amplifier, how are the capacitors treated? (0.5 M)
ii) When the emitter resistor is bypassed with a capacitor, how is the gain of the
amplifier affected? (0.5 M)
iii) What is the purpose of putting emitter resistor in the circuit? (1 M)
iv) What is the phase relationship of the input and output voltage of common emitter
amplifier? (0.5 M)
v) State the function of input and output coupling capacitor, CC1 & CC2. (0.5 M)
vi) Why do theoretical and practical values differ? (1 M)
6.
CONCLUSION
Make your overall conclusion by referring to the objective of this experiment (your
answer should be in simple notes).(3 M)

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