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1. Reverse saturation current of a common emitter transistor is
a) Collector current when emitter is open circuited and base-collector junction is reverse biased
b) Emitter current when collector is open circuited and base-collector junction is reverse biased
c) Base current when emitter circuit is open circuited and emitter-collector junction is reverse biased
d) Collector current when base circuit is open circuited

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Answer: a [Reason:] Reverse saturation current is the collector current when emitter is open circuited and base-collector junction is reverse bias mode. In this mode of operation collector-base junction act as a reverse biased diode. The current in this reverse biased junction is known as reverse saturation current.

2. Reverse collector saturation current ICBO is
a) Current when emitter current is zero
b) Current when base current is zero
c) Same as reverse saturation current
d) Current when either emitter or base current is zero

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Answer: A [Reason:] Reverse collector current ICBO is collector-base current when emitter is open. This is same as reverse saturation current in ideal but have slight difference in practical.

3. Reverse collector saturation is greater than Reverse saturation current because reverse collector saturation
a) Is ideal
b) Doesn’t include leakage current
c) They are same
d) Include avalanche multiplication current which is caused by the collision in collector junction

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Answer: d [Reason:] One of the reasons why reverse collector current exceeds the reverse saturation current is Introduction of avalanche multiplication current in the base collector junction. This happens when high energy electron collides in the lattice it creates more number of electron and thus a greater current.

4. Reverse collector saturation is greater than Reverse saturation current because reverse collector saturation
a) Is ideal
b) Consist leakage current flowing through junction and surface
c) Doesn’t include avalanche multiplication current opposing collector current
d) They are same

View Answer

Answer: b [Reason:] One of the reasons why reverse collector current exceeds the reverse saturation current is Introduction of avalanche multiplication current in the base collector junction. This happens when high energy electron collides in the lattice it creates more number of electron and thus a greater current. Another reason is leakage current flowing through junction and surface. The ICBO also counts leakage current flowing through junction and surface.

5. Which of the following statement about a common base transistor is true
a) Very low input impedance
b) Very low output Impedance
c) Current gain is greater than unity
d) Voltage gain is very low

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Answer: a [Reason:] Common base transistor has very low input resistance (20Ω). It also has very high output resistance. Its current gain is less than unity and it has a medium voltage gain.

6. Which of the following statement about a common emitter transistor is true
a) Very high input resistance
b) High output resistance
c) Current gain is less than unity
d) Voltage gain is very low

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Answer: b [Reason:] Common emitter transistor has high output resistance (about 40k). It has low input resistance (about 1k). Current gain is high (20 to few hundreds). Voltage gain is medium.

7. Which of the following statement about a common collector transistor is true
a) Very low input impedance
b) Very high output impedance
c) Very low current gain
d) Low voltage gain

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Answer: d [Reason:] common collector configuration has high input impedance and low output impedance. The current gain is high but voltage gain is low.

8. Which of the following configuration is used as input stage of multistage amplifier
a) Common base configuration
b) Common emitter configuration
c) Common collector configuration
d) All configurations are equally suited

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Answer: a [Reason:] Since input resistance is low and output resistance is high common base configuration is used as input stage of multistage amplifier. Common emitter configuration is used for audio signal amplification. Common collector is used for impedance matching.

9. Which of the following configuration is used for audio signal amplification
a) Common base configuration
b) Common emitter configuration
c) Common collector configuration
d) All configurations are equally suited

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Answer: b [Reason:] Common base configuration is used as input stage of multistage amplifier. Since voltage gain is high, common emitter configuration is used for audio signal amplification. Common collector is used for impedance matching.

10. Which of the following configuration is used for impedance matching
a) Common base configuration
b) Common emitter configuration
c) Common collector configuration
d) All configurations are equally suited

View Answer

Answer: c [Reason:] Common base configuration is used as input stage of multistage amplifier. Common emitter configuration is used for audio signal amplification. Since input impedance is high and output impedance is low, common collector is used for impedance matching.