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EE 330 Analog Electronics Laboratory
Fall 2012
Instructor- Fei Wang
Experiment #7Design of a Common-Emitter Biasing
Circuit
Date Performed: 11/12/2012
Date Submitted: 11/30/2012
By
James Fitzgerald
Larry Harmon
Vinh Kim
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Objective
The purpose of experiment #7 is to learn how to design a common emitter amplifier
circuit by selecting the right resistors values and supply voltage.
List of Instruments
1) Breadboard
2) 4 Resistors: 1.66M , 5M , 4.7k , and 2k .
3) Alligator Clips4) Jumper wires
5) Power supply
6) 2N2222
7) 10 F
8) Oscilloscope
PreLab
A. Using the circuit below we calculated a resistance for Rl that would give a gain greater
than 2.
Vi
10F
Vcc
RB1
RB2
RL
RE
VO
4.7 k
2N2222
F igure 1Common Emitter Amplifier
Using these design considerations, select values and VCCso that the amplifier meets the
following specifications:
1. The circuit must provide an output voltage swing Vo of 10 volts peak to peak with no
distortion of the Vowaveshape. Distortion is defined as limiting of Vodue to the amplifier
operating the transistor near cutoff or saturation regions.
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2. It must provide this distortion-free amplification over the temperature range from 25C to
100C, and for any value beta from betaminto betamaxfor the 2N2222.
3.
It must provide a gain, Vo/Vi, of at least 2.
RL/RE = 4.7 k / 1.68 k = 2.78
4. The required VCCis 20 volts or less.
Are VCC= 15V
5. RL= 4.68 k PL= 6.32 mW I = 1.162mA
RE= 1.69 k PE= 2.325 mW I = 1.173 mA
RB1= 103.2k PB1= 1.389 mW I = .116 mA
RB2= 24.4 k PB2= .269 mW I = .105 mA
VCC= 15 volts
What peak-to-peak value of Viis needed to provide 10 volts p-p output?
Vip-p= 3.8 volts
Set-up
1. Set up the circuit of Figure 1 using your 2N2222 with your values of resistors and VCC.
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2. Set the input voltage, Vi, to the peak to peak value necessary to yield 10 Vp-pat Vo.
3) Connect the oscilloscope to view Vo and Vi simultaneously. If you do not observe an
undistorted Vo, it will be necessary to tweak the values of resistance in order to yield a
distortionless output.
In order to maximize our output results we set the output and get distortion to give a
better idea the area where our max input should be.
4) Record VBE, IC, VCE, gain, and the waveshapes of Vo and Vi on the same time axis.
Label the Vo and Vi waveshapes with their maxima and minima values. Place your
results in Table 1.
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Results
Complete Table 1 below.
Source BETA VBE(V) VCE(V) IC(mA) GAIN
Calculated
Using Specified
Beta (Use beta
in datasheet)
Bmin
35 0.7 V 7.49 V 1.164 2.78
Calculated Using
Measured Beta
(Use your results
from Lab 6)
249 0.7 V 7.503V 1.173 2.78
Measurements 100 0.7 V 7.56V 1.162 2.625
Questions
1. What are possible causes of differences between the calculated and experimental values of
VCE and IC?
2. What change in ICO(ICBO) did you anticipate over the temperature range of 25C to 100C?
3. Calculate the theoretical quiescent collector power dissipation of your transistor with beta =
betamin.
.
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4. How would the voltage gain of your amplifier be affected by reducing the 10 microfarad
capacitor? Explain.
Conclusion
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