EE115A
Prof. Frank Chang
Winter2010
Homework #4
Due Tue, Feb 9th, 2010
Problem 1.
Fig 1.
For the circuit shown in figure 1, I
C
is designed to be 0.25mA.
Assume I
S
equals
6*10
16
A,
β
=100 and Early voltage
equals
∞
.
(a) Determine the required value of R
1
.
(b) What is the error in I
C
if R
E
deviates from its nominal value by 5%?
Problem 2.
Fig 2.
(a) Draw the smallsignal model for the circuit shown in figure 2.
(b) Find V
out
/V
in
.
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you don’t need to find the DC operating point for this problem and you may assume the
Early voltage is
∞
).
Problem 3.
Fig 3.
For the circuit shown in figure 3, the g
m
is designed to be 1/260
Ω
and if
β
= 100, I
S
= 2*10
17
A,
and Early voltage equals
∞
determine the required R
B,
operating point and the input impedance
looking into the base.
Problem 4.
Sketch the I
C
 V
CE
characteristics of an npn transistor having
β
=100 and Early voltage
=100V.
Sketch the characteristic curves for i
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 Winter '09
 KAISER
 Volt, Bipolar junction transistor, Smallsignal model, Early effect, early voltage

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