Transistor Audio Power Amplifiers Model(1st)

The most important consideration in power amplifier is ___________

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Biasing the circuit
Collector efficiency
To keep the transformer cool
None of the above

If the zero signal dissipation of a transistor is 1W, then power rating of the transistor should be at least ___________

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5 W
1 W
33 W
75 W

A 2-transistor class B power amplifier is commonly called ___________ amplifier

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Dual
Differential
Symmetrical
Push-pull

When no signal is applied, the approximate collector efficiency of class A power amplifier is

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0%
50%
10%
25%

An AF amplifier is shielded to ___________

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Prevent induction due to stray magnetic fields
Keep the amplifier cool
None of the above
Protect from rusting

The output stage of a multistage amplifier is also called ___________

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Mixer stage
Detector stage
F stage
Power stage

When a transistor is cut off___________

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Maximum current flows
Maximum voltage appears across load
Maximum voltage appears across transistor
None of the above

The output stage of a multistage amplifier usually employs ___________

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None of the above
Class A power amplifier
Push-pull amplifier
Preamplifier

___________ coupling is generally employed in power amplifiers

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Impedance
Transformer
direct
RC

The maximum a.c. power output from a class A power amplifier is 10 W. What should be the minimum power rating of the transistor used ?

1 Mark(s)

10 W
20 W
5 W
15 W

What turn ratio (Np/Ns) of transformer is required to match 4 Ω speaker to a transistor having an output impedance of 8000 O?

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2
None of the above
3
7

The most costly coupling is ___________ coupling

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RC
Direct
Impedance
Transformer

Low efficiency of a power amplifier results in ___________

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Low forward bias
More battery consumption
Less battery consumption
None of the above

If a transistor is operated in such a way that output current flows for 60° of the input signal, then it is ___________ operation

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None of the above
Class C
Class A
Class B

A class A power amplifier is sometimes called ___________ amplifier

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Differential
Symmetrical
Reciprocating
Single-ended

What will be the collector efficiency of a power amplifier having zero signal power dissipation of 5 watts and a.c. power output of 2 watts?

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80%
20%
40%
50%

Transformer coupling can be used in ___________ amplifiers

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None of the above
Only voltage
Only power
Either power or voltage

The output transformer used in a power amplifier is a ___________ transformer

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1:1 ratio
Step-down
None of the above
Step-up

If the power rating of a transistor is 1W and collector current is 100mA, then maximum allowable collector voltage is ___________

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20V
10V
1V
100V

Class ___________ operation gives the maximum distortion

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A
AB
B
C

Power amplifiers handle ___________ signals compare to voltage amplifiers

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Large
Small
Very small
None of the above

If the gain versus frequency curve of a transistor amplifier is not flat, then there is distortion.

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None of the above
Frequency
Amplitude
Intermodulation

For the same a.c. power output as above, what should be the minimum power rating of transistor for class B operation?

1 Mark(s)

10 W
4 W
None of the above
8 W

Class C power amplifier has the highest collector efficiency

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AB
B
C
A

The maximum efficiency of resistance loaded class A power amplifier is

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5%
25%
30%
50%

A transformer coupled class A power amplifier has a load of 100 Ω on the secondary. If the turn ratio is 10:1, what is the value of load appearing on the primary?

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5 kΩ
10 kΩ
100 kΩ
20 kΩ

In class A operation, the operating point is generally located ___________ of the d.c. load line.

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At saturation point
At cut off point
At the middle
None of the above

The disadvantage of impedance matching is that it ___________

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Requires a transformer
Gives low power output
Gives distorted output
None of the above

A class A power amplifier uses ___________

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None of the above
Three transistors
One transistor
Two transistors

The driver stage usually employs___________

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None of the above
Push-pull amplifier
Class C amplifier
Class A power amplifier

The maximum efficiency of transformer coupled class A power amplifier is ___________

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30%
45%
50%
80%

The pulsating d.c. applied to power amplifier causes ___________

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Excessive forward voltage
None of the above
Hum in the circuit
Burning of transistor

The maximum collector efficiency of class B operation is ___________

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90%
5%
50%
5%

Power amplifiers generally use transformer coupling because transformer per-mits

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Good frequency response
Distortionless output
Cooling of the circuit
Impedance matching

The class B push-pull circuit can deliver 100 W of a.c. output power. What should be the minimum power rating of each transistor?

1 Mark(s)

20 W
40 W
10 W
80 W

The size of a power transistor is made considerably large to ___________

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None of the above
Facilitate connections
Dissipate heat
Provide easy handling

A power amplifier has comparatively ___________ ß

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Very large
None of the above
Small
Large

The push-pull circuit must use ___________ operation

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Class B
Class A
Class AB
Class C

Transistor Audio Power Amplifiers Model(1st) : Question 1 of 38