Electronics and Communication Engineering - Electronic Devices and Circuits

26. 

The forbidden energy gap in semiconductors

A. is always zero
B. lies just below the valence band
C. lies between the valence band and the conduction band
D. lies just above the conduction band

Answer: Option C

Explanation:

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27. 

In commercial electron tubes the current produced by the cathode at 1000 K is about

A. 0.01 A per cm2 of cathode surface
B. 0.1 A per cm2 of cathode surface
C. 1 A per cm2 of cathode surface
D. 5 A per cm2 of cathode surface

Answer: Option B

Explanation:

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28. 

In a conductor the conduction and valence bands overlap

A. True
B. False

Answer: Option A

Explanation:

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29. 

In which of the following device electrons will be the majority carriers?

A. P-type semiconductor
B. N-type semiconductor
C. N-P-N transistor
D. P-N-P transistor

Answer: Option D

Explanation:

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30. 

An n channel JFET has IDS whose value is

A. maximum for VGS = 0 and minimum for VGS negative and large
B. minimum for VGS = 0 and maximum for VGS negative and large
C. maximum for VGS = 0 and minimum for VGS positive and large
D. minimum for VGS = 0 and maximum for VGS positive and large

Answer: Option A

Explanation:

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