CET Semiconductor Devices & Circuits 3

Question 1

What is the depletion region in a p-n junction?

Accepted Answer

The region devoid of mobile charge carriers near the junction

Answer

The depletion region forms at the p-n junction when electrons and holes recombine, leaving an area with no free charge carriers.

Question 2

Which of the following describes the operation of an enhancement-mode NMOS transistor when VGS = 0?

Accepted Answer

Channel does not exist (OFF)

Answer

An enhancement-mode NMOS has no channel when VGS = 0; a positive gate voltage must exceed the threshold to create the channel.

Question 3

The breakdown mechanism in heavily doped, thin-junction diodes at low reverse voltages is called:

Accepted Answer

Zener breakdown

Answer

Zener (or tunneling) breakdown occurs in heavily doped junctions where the strong electric field allows electrons to tunnel through the narrow barrier.

Question 4

In a common-emitter amplifier, what is the phase relationship between the input and output signals?

Accepted Answer

180° out-of-phase

Answer

The common-emitter configuration inverts the signal, producing a 180° phase shift between base input and collector output.

Question 5

A varactor diode is used primarily as a:

Accepted Answer

Voltage-controlled capacitor

Answer

A varactor (varicap) diode's depletion-region width changes with reverse bias, varying its junction capacitance for tuning applications.

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CET Semiconductor Devices & Circuits 3