Transistor Audio Power Amplifiers MCQs with Explanations

Transformer coupling is commonly used in power amplifiers because it offers several advantages: * Impedance Matching: Transformers can efficiently match the high output impedance of the power amplifier to the low impedance of the loudspeaker. This maximizes power transfer to the load (speaker). * DC Isolation: Transformers provide DC isolation between the amplifier stage and the load. * Efficiency: Although transformers can introduce some losses, they generally offer better efficiency in impedance matching compared to other coupling methods for power amplifiers. Let's look at why the other options are less suitable for power amplifiers: * RC Coupling: While simple and inexpensive, RC coupling suffers from significant power loss and poor impedance matching, making it less suitable for power amplifiers where efficiency is crucial. * Direct Coupling: Direct coupling can be challenging due to DC offset issues and the potential for damaging the loudspeaker with DC current. * Impedance Coupling: While impedance coupling can refer to using inductors or tuned circuits, it's not as widely used as transformer coupling in general power amplifier designs, especially for audio frequencies and can be complex.

Push-pull amplifier is the correct answer to “The output stage of a multistage amplifier usually employs ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

20 W is the correct answer to “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”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

25% is the correct answer to “The maximum efficiency of resistance loaded class A power amplifier is”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Gives distorted output is the correct answer to “The disadvantage of impedance matching is that it ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

At the middle is the correct answer to “In class A operation, the operating point is generally located ___________ of the d.c. load line.”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Step-down is the correct answer to “The output transformer used in a power amplifier is a ___________ transformer”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Either power or voltage is the correct answer to “Transformer coupling can be used in ___________ amplifiers”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Push-pull is the correct answer to “A 2-transistor class B power amplifier is commonly called ___________ amplifier”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Single-ended is the correct answer to “A class A power amplifier is sometimes called ___________ amplifier”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Class C is the correct answer to “If a transistor is operated in such a way that output current flows for 60° of the input signal, then it is ___________ operation”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Class B is the correct answer to “The push-pull circuit must use ___________ operation”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Transformer is the correct answer to “The most costly coupling is ___________ coupling”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

0% is the correct answer to “When no signal is applied, the approximate collector efficiency of class A power amplifier is”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

1 W is the correct answer to “If the zero signal dissipation of a transistor is 1W, then power rating of the transistor should be at least ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

5% is the correct answer to “The maximum collector efficiency of class B operation is ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

C is the correct answer to “Class C power amplifier has the highest collector efficiency”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

C is the correct answer to “Class ___________ operation gives the maximum distortion”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Prevent induction due to stray magnetic fields is the correct answer to “An AF amplifier is shielded to ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

20 W is the correct answer to “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”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

One transistor is the correct answer to “A class A power amplifier uses ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

50% is the correct answer to “The maximum efficiency of transformer coupled class A power amplifier is ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Collector efficiency is the correct answer to “The most important consideration in power amplifier is ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

7 is the correct answer to “What turn ratio (Np/Ns) of transformer is required to match 4 Ω speaker to a transistor having an output impedance of 8000 Ω”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Dissipate heat is the correct answer to “The size of a power transistor is made considerably large to ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

10V is the correct answer to “If the power rating of a transistor is 1W and collector current is 100mA, then maximum allowable collector voltage is ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Power stage is the correct answer to “The output stage of a multistage amplifier is also called ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Large is the correct answer to “Power amplifiers handle ___________ signals compare to voltage amplifiers”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Hum in the circuit is the correct answer to “The pulsating d.c. applied to power amplifier causes ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

4 W is the correct answer to “For the same a.c. power output as above, what should be the minimum power rating of transistor for class B operation”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

40% is the correct answer to “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”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

10 kΩ is the correct answer to “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”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Maximum voltage appears across transistor is the correct answer to “When a transistor is cut off___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

More battery consumption is the correct answer to “Low efficiency of a power amplifier results in ___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Frequency is the correct answer to “If the gain versus frequency curve of a transistor amplifier is not flat, then there is distortion.”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Small is the correct answer to “A power amplifier has comparatively ___________ ß”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Impedance matching is the correct answer to “Power amplifiers generally use transformer coupling because transformer per-mits”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.

Class A power amplifier is the correct answer to “The driver stage usually employs___________”. This question is standard in competitive examination syllabi for Transistor Audio Power Amplifiers.