1987
1.
In case of class A amplifiers, the
ratio of efficiency of transformer coupled amplifier to efficiency of a
transformer less amplifier is
a.
2.0
b.
1.36
c.
1.0
d.
0.5
Answer: A
1990
1.
A pick up signal is power amplified
using a complementary symmetry push pull amplifier and fed to a 5 Ω
loud speaker as shown.
The specifications of power
transistors are as follows:
ICmax = Maximum collector
current = 2 Amps and PCmax = Maximum power dissipation = 1 Watt.
Find the maximum power delivered to
the loud speaker, if the maximum output voltage subject to OP-AMP voltage
limitations is 15 volts.
If the transistors are mounted on a
heat sink, so that PCmax changes to 3 Watts. What will be the new
value of the maximum power delivered?
Answer: (i) 3.08 Watts, circuit gets breakdown (ii) 3.08 Watts, circuit gets breakdown
1993
1.
In a transistor push-pull amplifier
a.
there is no DC present at the output
b.
there is no distortion in the output
c.
there are no even harmonics in the
output
d.
there are no odd harmonics in the
output
Answer: C
Solution :
https://www.youtube.com/watch?v=BFUb9gQdKoM
1994
1.
A class-A transformer coupled
transistor power amplifier is required to deliver a power output of 10 watts.
The maximum power rating of the transistor should not be less than ______
a.
5 watts
b.
10 watts
c.
20 watts
d.
40 watts
Answer: C
2.
In order to reduce the harmonic distortion
in an amplifier, its dynamic range has to be _________
Ans : Dynamic
Range expressed in decibels (dB), is the ratio of the highest signal
level a circuit, component, or system can handle, to the lowest signal level it
can handle. Several parameters can be used to define the highest-level signal,
such as the 1-dB compression point as well as the TOi point.
The lowest level signal level is limited by output noise, while the highest level signal is limited most often by distortion.
The 1-dB compression point for an amplifier, for example, is where the linearity of the component begins to degrade. Under linear conditions, a 1-dB rise in input power will result in a 1-dB increase in output power. When the increase at the output is 1-dB less than the increase at the input, it is said to be the amplifier's 1-dB compression point.
The lowest level signal level is limited by output noise, while the highest level signal is limited most often by distortion.
The 1-dB compression point for an amplifier, for example, is where the linearity of the component begins to degrade. Under linear conditions, a 1-dB rise in input power will result in a 1-dB increase in output power. When the increase at the output is 1-dB less than the increase at the input, it is said to be the amplifier's 1-dB compression point.
High Dynamic Range Amplifiers have low noise figures, low
gain, low distortion and high 1 dB compression points. This combination of
performance characteristics provides the greatest range between the minimum
detectable signal and the signal level that will start to compress the
amplifier. So in order to reduce the harmonic distortion in an amplifier, its
dynamic range has to be compressed to 1-dB
compression point.
3.
For the 2N338 transistor, the
manufacturer specifies Pmax = 100 mW at 25oC, free air
temperature and the maximum junction temperature Tjmax = 125oC.
Its thermal resistance is ________
Answer: 1000 oC/W
1995
1.
A power amplifier delivers 50W
output at 50% efficiency. The ambient temperature is 25oC. If the
maximum allowable junction temperature is 150oC, then the maximum
thermal resistance øjc
that can be tolerated is __________
Answer: 2.5 oC/W
1998
1.
A distorted sinusoid has the
amplitudes A1, A2, A3 … of the fundamental,
second harmonic, third harmonic, …..respectively. The total harmonic distortion
is
Answer: B
Solution : https://www.youtube.com/watch?v=jLPkLCkKXRc
1999
1.
Crossover distortion behavior is
characteristic of
a.
Class A output stage
b.
Class B output stage
c.
Class AB output stage
d.
Common base output stage
Answer: B
Solution
: https://www.youtube.com/watch?v=1ussDIU0A0E
If the transistors are mounted on a heat sink, so that PCmax changes to 3 Watts. What will be the new value of the maximum power delivered? Satılık Elektronik
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