EE 541
USC Viterbi School of Engineering
J. Choma
Homework #01
1
Fall Semester, 2011
U
niversity of
S
outhern
C
alifornia
USC Viterbi School of Engineering
Ming Hsieh Department of Electrical Engineering
EE 541:
Homework Assignment #01
Fall, 2011
Due: 08/31/2011
Choma
Problem #01:
The model shown within the symbolic network “box” in Figure (P1) is a small
signal, and therefore linear, equivalent circuit of an emitter-degenerated, common emitter am-
plifier.
The amplifier is driven by a voltage source whose Thévenin resistance is
R
s
, and its load
termination consists of a resistance,
R
l
in shunt with a capacitance,
C
l
.
In this problem,
R
s
= 50
, R
l
= 1.2 K
, R
e
= 120
, and
C
l
= 300 fF
.
The transistor model parameters are
r
b
= 120
,
r
= 3.3 K
, r
o
= 18 K
, and
= 220 amps/amp
.
I
V
s
R
s
R
e
r
b
r
C
l
R
l
I
r
o
I
2
V
2
I
1
V
1
R
out
R
in
Figure (P1)
(a).
Derive analytical expressions for each of the four h-parameters of the degenerated common
emitter amplifier.
(b).
Using the h-parameter expressions deduced in Part (a), derive analytical expressions for
the low frequency, open loop values of voltage gain,
V
2
/V
s
, input resistance,
R
in
, and output
resistance,
R
out
.
(c).
Using the h-parameter expressions deduced in Part (a), derive an analytical expression for
the low frequency loop gain of the amplifier.
Discuss the influence that the emitter degen-
eration resistance,
R
e
, has on this loop gain.
(d).
Using appropriate preceding results, compute numerical, low frequency values for:
i.
the open loop input resistance;
ii.
the driving point input resistance;
iii.
the open loop output resistance;
iv.
the driving point output resistance;
v.
the loop gain;
vi.
the open loop voltage gain;
vii.
the closed loop voltage gain.