1995
4.
An NPN transistor under forward
active mode of operation is biased at Ic = 1 mA, and has a total
emitter base capacitance CK of 12 pF, and the base transit time τF of 260
psec. Under this condition, the depletion capacitance of the emitter base
junction is _____________
Answer: 2 pF
1996
19. A common emitter amplifier with an external capacitors CC
connected across the base and the collector of the transistor is shown. Given gm
= 5 mA/V, rπ
= 20 kΩ,
Cπ
= 1.5 pF and Cµ
= 0.5 pF.
a.
Determine the ac small signal mid
band voltage gain, Vo/Vs.
b.
Determine the upper cutoff frequency
fH of the amplifier.
Answer: (a) -33.33 (b) 18.326 KHz
1998
1.
The fτ of a BJT is related to its gm, Cπ and Cµ
as follows
Answer: D
1999
4.
An NPN transistor (with C = 0.3 pF)
has a unity gain cutoff frequency fτ of 400 MHz at a dc bias current IC = 1 mA. The
value of its Cµ
(in pF) is approximately (VT = 26 mV)
a.
15
b.
30
c.
50
d.
96
Answer: A
6.
An amplifier is assumed to have a
single pole high frequency transfer function. The rise time of its output
response to a step function input is 35 nsec. The upper -3 dB frequency (in
MHz) for the amplifier to a sinusoidal input is approximately at
a.
4.55
b.
10
c.
20
d.
28.6
Answer: B
2000
4.
The current gain of a bipolar
transistor drops at high frequencies because of
a.
Transistor capacitances
b.
High current effects in the base
c.
Parasitic inductance effects
d.
The Early Effect
Answer: A
2001
4.
An NPN BJT has gm = 38
mA/volt, Cµ
= 10-14 F, Cπ
= 4x10-13 F and DC current gain β = 90. For this transistor fτ and fβ
are
a.
fτ = 1.64 x 108
Hz and fβ
= 1.47 x 1010 Hz
b.
fτ = 1.47 x 1010
Hz and fβ
= 1.64 x 108 Hz
c.
fτ = 1.33 x 1012
Hz and fβ
= 1.47 x 1010 Hz
d.
fτ = 1.47 x 1010
Hz and fβ
= 1.33 x 1012 Hz
Answer: B
2003
5.
Generally, the gain of a transistor
amplifier falls at high frequencies due to the
a.
Internal capacitance of the device
b.
Coupling capacitor at the input
c.
Skin effect
d.
Coupling capacitor at the output
Answer: A
12. An ideal saw-tooth voltages waveform of frequency of 500 Hz
and amplitude 3 volts is generated by charging a capacitor of 2 µF in every cycle. The charging requires
a.
Constant voltage source of 3 volts
for 1 ms
b.
Constant voltage source of 3 volts
for 2 ms
c.
Constant current source of 1 mA for
1 ms
d.
Constant current source of 3 mA for
2 ms
Answer: D
2010
Common
Data Questions:
Consider the common emitter amplifier shown below with the
following circuit parameters.
β = 100, gm = 0.3861 A/V, ro = 259 Ω, RS = 1 KΩ, RB = 93 KΩ, RC = 250 Ω, RL = 1 KΩ, C1 = ∞ and C2 = 4.7 µF.
5.
The resistance seen by the source VS
is
a.
258 Ω
b.
1258 Ω
c.
93 KΩ
d.
∞
Answer: B
6.
The lower cutoff frequency due to C2
is
a.
33.9 Hz
b.
27.1 Hz
c.
13.6 Hz
d.
16.9 Hz
Answer: B
2015
3. At
very high frequencies, the peak output voltage Vo (in volts) is
______________
Answer: 0.5
Solution: https://www.youtube.com/watch?v=_O4UfZGA87c
Solution: https://www.youtube.com/watch?v=_O4UfZGA87c
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