FREE BEE Bachelor of Electrical Engineering Semiconductor Devices and Circuits Questions and Answers Flashcards

What is the threshold voltage shift caused by the body effect in a MOSFET?

Answer: Threshold voltage increases when source-to-body voltage increases

The body effect increases the threshold voltage when a reverse bias is applied between the source and body terminals due to wider depletion in the substrate.

Which parameter describes the efficiency of a BJT in transferring carriers from emitter to collector?

Answer: Common-base current gain (alpha)

The common-base current gain alpha represents the fraction of emitter current that reaches the collector, typically very close to unity.

What is the dominant carrier transport mechanism in the base region of a bipolar junction transistor?

Answer: Diffusion

Minority carriers injected into the thin, lightly doped base region travel primarily by diffusion due to the concentration gradient.

In a CMOS inverter, what is the static power dissipation when the output is at a stable logic level?

Answer: Nearly zero

In a stable state, one transistor is fully on and the other is fully off, so there is no direct path from VDD to ground and static power is nearly zero.

What determines the built-in potential of a p-n junction at thermal equilibrium?

Answer: Doping concentrations on both sides

The built-in potential depends on the logarithm of the product of donor and acceptor doping concentrations divided by the intrinsic carrier concentration squared.

Which effect in a short-channel MOSFET causes the threshold voltage to decrease as the channel length is reduced?

Answer: Drain-induced barrier lowering

Drain-induced barrier lowering (DIBL) reduces the source-side potential barrier as the drain field penetrates closer to the source in short channels, lowering threshold voltage.