CHAPTER 8
COMMON EMITTER AMPLIFIER
8.1
Overview
You will design, simulate, build the circuit, and measure the voltage gain of the
amplifier.
8.2
Cadence Simulation
1. The specifications for the common-emitter amplifier are shown below
gm =19.2 mS
VRE =0.3 V
I1 = 40IB
VCC = 9V
Vin,m = 10 mV
2. Assume that the 2N3904 transistor have a β = 150 and an IS of 6.734 fA.
Electronics I Laboratory Manual, First Edition.
c 2014 ,J. Ou.
Copyright 41
42
COMMON EMITTER AMPLIFIER
RC
R1
+
9V − VCC
2N 3904
1kHz
100mVpp
C1
R2
Vs
RE
Figure 8.1: Common-emitter amplifier
3. Determine IC from gm .
gm = IC /VT
(8.1)
4. Determine RE from the VRE specification.
RE = VRE /IC
5. Calculate VBE .
(8.2)
IC
)
IS
(8.3)
VB = VBE + VRE
(8.4)
VBE = VT ln(
6. Calculate the voltage at VB .
7. Determine IB from β and IC .
8. Determine I1 given IB .
9. Determine R1 + R2 from VCC and I1 .
I1 = VCC /(R1 + R2 )
(8.5)
10. Determine R2 from VB .
VB =
R2
VCC
R1 + R2
11. Determine R1 from R1 + R2 and R2 .
(8.6)
IMPLEMENTATION
43
12. Choose RC so as to have a collector voltage of VCC /2.
VCC − RC IC = VCC /2
(8.7)
13. Design the value of coupling capacitor so that the impedance of the capacitor is
less than 5 Ohms.
1
|
(8.8)
|Zc | = |
ωC1
14. Calculate the gain of the amplifier.
AV = −
RC
1/gm + RE
(8.9)
15. Simulate the circuit in Cadence.
16. Submission checklist
A table summarizing calculated and simulated values of IC , VBE , VB , IB ,
I1 , VRE , and AV .
Simulated Vin and Vout .
8.3
Implementation
1. Build the circuit in the lab.
2. Measure the current in the RC by dividing VRC by RC .
3. Measure the DC voltage at the base of the transistor.
4. Measure VRE
5. Measure the peak-to-peak voltage of Vin and Vout on the oscilloscope.
6. Submission checklist
A table summarizing simulated and measured values of IC , VBE , VB , IB ,
I1 , VRE , and AV .
Measured plots of Vin and Vout (hint: save the oscilloscope image onto a
USB drive).