1. The use of amplifier in a circuit is to _____________ for input signal
a) Provide a phase shift
b) Provide strength
c) Provide frequency enhancement
d) Make circuit compatible
Answer: b [Reason:] The only use of amplifier in a circuit is to provide strength to signal.
2. The unwanted characteristics of amplifier output apart from desired output is collectively termed as
Answer: d [Reason:] The unwanted characteristics of amplifier output apart from desired output is collectively termed as distortion. This should be avoided.
3. Unit of power rating of a transistor is expressed in
Answer: a [Reason:] Power rating is the maximum power allowable to dissipate by a transistor beyond this point transistor may behave unlikely. This is expressed in watts.
4. Which device is used for the amplification of audio signal before power amplifiers
c) Vacuum tubes
Answer: c [Reason:] Before invention of power amplifier vacuum tubes are used for audio signal amplification which consumes large space and costly.
5. Power amplifier directly amplifies
a) Voltage of signal
b) Current of the signal
c) Power of the signal
d) All of the mentioned
Answer: d [Reason:] Power amplifier increases voltage as well as current. Increase in voltage or current is small compared to normal amplifiers. But power amplification is occurred ie. Voltage x current is more.
6. Input stage of power amplifier is also called
a) First op
b) Beginning stage
c) Front end
d) Normal stage
Answer: c [Reason:] Input stage of power amplifier is also called front end.
7. Transistor in power amplifier is
a) An active device
b) A passive device
c) A op-amp
d) A voltage generating device
Answer: a [Reason:] Transistor is an active device since transistor contain voltage sources which is necessary for amplification.
8. For a perfect power amplifier output power rating will be ________ if output impedance is halved.
d) Square rooted
Answer: c [Reason:] Since in the equation of power output power is proportional to current square and inversely proportional to resistance. Power will be doubled.
9. Which of the following audio speaker will be hard to be driven by a power amplifier
Answer: d [Reason:] If the resistance of audio amplifier is less, the output power of the transistor will be high since output current is increasing. Hence to drive 2ohm speaker amplifier needs double power that for 4ohm speaker.
10. The power rating of amplifier is 100watts then the transistor can only operate at
a) Power higher than 100w
b) Power lower than 100w
c) Power near to 100w
d) Power lower than 50w
Answer: b [Reason:] The power rating of transistor is the maximum allowable power usage of a transistor beyond that transistor may damage. Last option may be correct if the word “only” is not in the question.