ISCET Semiconductor Device Principles 4

Question 1

What is the purpose of the intrinsic layer in a PIN diode?

Accepted Answer

To provide a wide depletion region that reduces junction capacitance and enables fast switching at RF frequencies

Answer

The intrinsic (I) layer widens the depletion region, lowering capacitance and allowing PIN diodes to function as RF switches or attenuators.

Question 2

In a common-emitter BJT amplifier, which parameter is primarily responsible for the upper cutoff frequency limitation at high frequencies?

Accepted Answer

Miller-multiplied collector-base capacitance (Cµ)

Answer

The Miller effect multiplies the collector-base capacitance Cµ by (1 + |Av|), creating a dominant pole that limits high-frequency response.

Question 3

What does the threshold voltage (VTH) of a MOSFET depend on?

Accepted Answer

Gate oxide thickness, substrate doping, flat-band voltage, and oxide charge

Answer

VTH is determined by oxide thickness (tox), substrate doping (NA), flat-band voltage (VFB), and interface/oxide charges.

Question 4

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

Accepted Answer

It is a metal-semiconductor junction with majority carrier conduction and no minority carrier storage

Answer

Schottky diodes are metal-semiconductor junctions relying on majority carriers, eliminating minority carrier storage and enabling very fast switching.

Question 5

The small-signal output resistance (ro) of a BJT in the common-emitter configuration is approximately:

Accepted Answer

VA / IC

Answer

The output resistance ro ≈ VA / IC, where VA is the Early voltage and IC is the quiescent collector current.

(ISCET) International Society of Certified Electronics Technicians Practice Test

(ISCET) International Society of Certified Electronics Technicians Practice Test

ISCET Semiconductor Device Principles 4