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WorksheetsMCQs on Power Amplifiers
Total questions: 25
Worksheet time: 8mins
For class B operation, the collector current flows for
The whole cycle
Half the cycle
Less than half a cycle
Less than a quarter of a cycle
Transformer coupling is an example of
Direct coupling
AC coupling
DC coupling
Impedance coupling
An audio amplifier operates in the frequency range of
0 to 20 Hz
20 Hz to 2 kHz
20 to 20 kHz
Above 20 kHz
A tuned RF amplifier is
Narrowband
Wideband
Direct-coupled
A dc amplifier
The first stage of a preamp is
A tuned RF stage
Large signal
Small signal
A dc amplifier
For maximum peak-to-peak output voltage, the Q point should be
Near saturation
Near cutoff
At the center of the ac load line
At the center of the dc load line
Push-pull is almost always used with
Class A
Class B
Class C
All of the above
One advantage of a class B push-pull amplifier is
No quiescent current drain
Maximum efficiency of 78.5 percent
Greater efficiency than class A
All of the above
Class C amplifiers are almost always
Transformer-coupled between stages
Operated at audio frequencies
Tuned RF amplifiers
Wideband
The collector current of a class C amplifier
Is an amplified version of the input voltage
Has harmonics
Is negatively clamped
Flows for half a cycle
The bandwidth of a class C amplifier decreases when the
Resonant frequency increases
Q increases
Inductive reactance decreases
Load resistance decreases
The power rating of a transistor can be increased by
Raising the temperature
Using a heat sink
Using a derating curve
Operating with no input signal
The AC load line is the same as the DC load line when the AC collector resistance equals the
DC emitter resistance
AC emitter resistance
DC collector resistance
Supply voltage divided by collector current
If Rc = 100 Ω and Re = 180 Ω, the AC load resistance equals
64 Ω
90 Ω
100 Ω
180 Ω
The AC load line usually
Equals the DC load line
Has less slope than the DC load line
Is steeper than the DC load line
Is horizontal
In a class A amplifier, the collector current flows for
Less than half the cycle
Half the cycle
Less than the whole cycle
The entire cycle
With class A, the output signal should be
Unclipped
Clipped on positive voltage peak
Clipped on negative voltage peak
Clipped on negative current peak
The instantaneous operating point swings along the
AC load line
DC load line
Both load lines
Neither load line
The current drain of an amplifier is the
Total AC current from the generator
Total DC current from the supply
Current gain from base to collector
Current gain from collector to base
The power gain of an amplifier
Is the same as the voltage gain
Is smaller than the voltage gain
Equals output power divided by input power
Equals load power
Heat sinks reduce the
Transistor power
Ambient temperature
Junction temperature
Collector current
When the ambient temperature increases, the maximum transistor power rating
Decreases
Increases
Remains the same
None of the above
If the load power is 300 mW and the DC power is 1.5 W, the efficiency is
0
2 percent
3 percent
20 percent
The maximum efficiency of a class B push-pull amplifier is
25 percent
50 percent
78.5 percent
100 percent
A small quiescent current is necessary with a class AB push-pull amplifier to avoid
Crossover distortion
Destroying the compensating diodes
Excessive current drain
Loading the driver stage
