University of KwaZulu-Natal
Analogue Electronics 2 ENEL3AE
Exercises: Freq. Resp.
Exercises: Chap. 1: Frequency Response
Exercise 2:
(page 8)
The amplifier circuit shown is biased to operate at ID = 1 mA and
gm = 1 mA/V.
+ VDD
RD
10 k
Neglecting ro find the midband voltage gain AM = vo / vi.
Find the value of CS that places the corresponding pole at 10 Hz.
What is the frequency of the transfer-function zero introduced by CS?
Give an expression for the gain function Vo(s)/Vi(s).
What is the voltage gain of the amplifier at dc?
vo
CS
vi
RS
6 k
 VSS
Exercise 3:
(page 10)
For the CE amplifier circuit shown, the given BJT data
is: I E  0,33 mA ;   120; rx  50 ; VA  100 V .
Find the midband voltage gain AM = vo / vs, the low
−3 dB corner frequency fL and the frequency of the
zero due to CE.
Redesign the values of the capacitors to make
fL ≈ 100 Hz using the design approach suggested.
+5V
R1
4.7k
33k
Rs
5k
vs
C1
C2
vo
1F
1F
RL
5.6k
R2
RE
22k
Exercise 4:
(page 19)
For the CE amplifier circuit shown assume the BJT has
fT = 700 MHz and Cob = 1 pF, other data as in Ex 3.
Find the high −3 dB corner frequency fH using Miller’s
theorem and the method of OCTC.
Exercise 5:
(page 21)
For the CB amplifier circuit shown, the following
BJT data is given:
I E  0,33mA;   120;
RC
CE
3.9k
10F
+5V
RC
R1
4.7k
33k
vo
1F
C1
f T  700MHz; C ob  1pF
C2
1F
CE
10F
Find the input resistance Rin seen by the source
and the midband voltage gain AM = vo / vs.
R2
22k
vs
RL
5.6k
RE
3.9k
Estimate the location of the two poles and the
upper −3 dB corner frequency fH.
Rs
75
Rin
Exercise 6:
(page 23)
Refer to the emitter-follower circuit on page 22. Take RS = RL = 1 kΩ.
The BJT is biased at IC = 1 mA, and has β = 100, rx = 100 Ω, Cµ = 0,1 pF, fT = 2 GHz and VA = 20 V.
Determine the midband voltage gain AM = vo / vsig and the frequency of the dominant high-frequency pole.
V M Srivastava
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