BEE Semiconductor Devices and Electronics 4

Question 1

The channel length modulation parameter λ in a MOSFET affects which characteristic?

Accepted Answer

The slope of ID vs. VDS in the saturation region

Answer

Channel length modulation (λ) causes a slight increase in drain current with VDS in saturation, giving ID a finite slope rather than being flat.

Question 2

In a common-base BJT amplifier, the current gain (α) is always:

Accepted Answer

Less than 1 but close to 1

Answer

Alpha α = IC/IE < 1 because IE = IC + IB and some base current is lost, but α is typically 0.95–0.999.

Question 3

A Schottky diode differs from a standard p-n junction diode primarily because it:

Accepted Answer

Uses a metal-semiconductor junction and has faster switching with lower forward voltage

Answer

Schottky diodes form metal-semiconductor junctions, resulting in majority-carrier conduction, ~0.3 V forward drop, and very fast switching.

Question 4

The substrate bias effect (body effect) in a MOSFET causes the threshold voltage to:

Accepted Answer

Increase as substrate reverse bias increases

Answer

Increased reverse substrate bias widens the depletion region, requiring more gate voltage to invert the channel, raising VT.

Question 5

Which configuration of an op-amp has the highest input impedance and unity voltage gain?

Accepted Answer

Voltage follower (unity-gain buffer)

Answer

The voltage follower connects the output directly to the inverting input, achieving unity gain with ideally infinite input impedance.

BEE - Bachelor of Electrical Engineering Practice Test