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1. THD+N is a scale used to expressing _______ of an audio amplifier
a) Gain
b) Sound quality
c) Amplification factor
d) Distortion

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Answer: b [Reason:] THDN is a scale used to express sound quality of an audio amplifier. THD+N is measured using distortion analyzer.

2. THD is a measure of
a) Amount of harmonic content present in signal
b) Amount of output power
c) Total amount of distortion
d) Total amount of amplitude distortion

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Answer: a [Reason:] THD or total harmonic distortion is a measure amount of harmonic content resent in a signal.

3. The ratio of the RMS amplitude of the higher order harmonic frequencies to the RMS amplitude of the fundamental frequency is commonly called
a) Total harmonic power
b) Total amplitude distortion
c) Total frequency distortion
d) Total harmonic distortion

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Answer: d [Reason:] THD is the ratio of RMS amplitude of higher order harmonic frequencies to the RMS amplitude of the fundamental frequency. THD is expressed in percentage.

4. Intermodulation distortion is caused by
a) Presence of harmonic components in signal
b) Non- linearity of biasing circuit
c) Non-linearity of amplifier
d) High frequency signal

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Answer: c [Reason:] Intermodulation distortion is caused by non-linearity of amplifier. Therefore, this is a problem arises in real life implementation.

5. The ratio of the RMS value of additional frequency components in output to the RMS value of the original output of amplifier is called as
a) Intermodulation distortion
b) Total amplitude distortion
c) Total frequency distortion
d) Total harmonic distortion

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Answer: a [Reason:] The ratio of the RMS value of additional frequency components in output to the RMS value of the original output of amplifier is known as intermodulation distortion.

6. Second order harmonic distortion is
a) Amount of second harmonics and first harmonics in signal
b) Amount of second harmonics and fourth harmonics in signal
c) Amount of second harmonics present in signal
d) RMS value of all even harmonics in signal

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Answer: c [Reason:] Second harmonic distortion is the amount of second harmonic signal present in signal. It is important since second harmonic is most troublesome among other harmonics.

7. Power delivered to load is _________ with increase in harmonic distortion.
a) Increases
b) Decreases
c) Constant
d) Cannot predict

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Answer: a [Reason:] The equation of output power (Pac)D = Pac (1+D2). It is clear that output power increases with distortion.

8. In three-point method the harmonics which are considered for calculating distortion is
a) First harmonics only
b) First and Second harmonics only
c) First, Second and Third harmonics only
d) Second and Third harmonics only

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Answer: b [Reason:] In tree-point method, the distortion due to first and second harmonics is considered.

9. If D1, D2, D3, D4 are the distortion produced by second, third, fourth, fifth respectively (others are insignificant). Then total harmonic distortion is
a) √(D12+D22+D32+D42)
b) √(D12+D32)
c) √(D22+D42)
d) √(D12+D22)

View Answer

Answer: a [Reason:] Resultant harmonics is RMS value of individual harmonics.

10. Power delivered to load calculated by five-point method can be equal to
(Pac is power delivered to load without distortion and D is the RMS of all Harmonic distortion)
a) Pac (1-D2)
b) Pac /D2
c) Pac (1+D2)
d) Pac D2

View Answer

Answer: c [Reason:] Equation of power delivered to load is same whether it is calculated by three-point or five point. The only difference is calculation of D.