Sacramento State
College of Engineering and Computer Science
Department of Electrical and Electronic Engineering
CPE 102-01, Analog/Digital Electronics, Spring 2007
Homework #5 (Due Wednesday 5/16/07) Problem 1 is worth 8 points. Each of the others
is worth 3 points. Show all work.
1. (8 pts.) Calculate the ac voltage gain (AV) of the "common emitter" amplifier shown in
the figure below. Assume βF = βo = 210, VA = 90, and Is = 3.5x10-14 A for the transistor.
Assume the following values for the resistor circuit components: RS = 50 Ω, R1 = 3.3 kΩ,
R2 = 2.2 kΩ, RC = 47 Ω, RE = 33 Ω, R3 = 1 kΩ. Assume VCC = 35 V and all Cs are large
enough (~ ∞). What is the largest amplitude input signal |vs| that this amplifier could
accommodate without producing “clipping” of the output signal?
RC
R2
vo
+
C
RS
+
vs
VCC
C
-
C
RE
R1
R3
2. Assume the Op-amp in the figure below has "ideal" characteristics and find an expression
for the voltage transfer function (AV = vo /vs ) or “ac gain” for the circuit. (Consider both
magnitude and phase as functions of frequency.) What function does this circuit
perform? R1 = 5.6 KΩ, R2 = 18 KΩ, RS = 56 KΩ, C = 0.015 µF.
v~s
+
RS
C
~
vo
R2
R1
1
3. Assume the Op-amps in the figure below have "ideal" characteristics except for a finite
common mode rejection ratio (CMRRdB = 89). Let the Rs be precisely matched values,
with R = 100 kΩ. Let and R1 = 33 Ω and R2 = 12 kΩ. Determine the following
parameters: a. Adm (the differential mode gain of the circuit) and b. Acm (the common
mode gain of the circuit). [Hint: Section 11.4.6 of the text could prove helpful here!]
R
R
+
+
-
vo
R
v
dm
+
R1
R2
vcm
-
+
R2
R
+
4. Assume the Op-amps in the figure below have "ideal" characteristics. Determine
“transresistance” (RT = vo/IS in ohms) of the circuit. Let R1, = 10 kΩ, R2, = 22 kΩ, and Rf
= 10 MΩ. Can you see why this circuit is called a “current-to-voltage converter”?
Rf
+
v
-
o
Is
+
R1
2
R2
5. Analyze the Digital-to-Analog Converter (DAC) circuit in the diagram below. “Bit
switch settings are fixed as indicated in this circuit. Determine its output voltage with
these switch settings and its input resistance. What would the input resistance be if each
bit switch were changed to its complementary setting?
12 KΩ
24 KΩ
12 KΩ
24 KΩ
24 KΩ
24 KΩ
5V
12 KΩ
+
-
Vo
+
3