BEE Semiconductor Devices and Electronics 5

Question 1

Which semiconductor device is best suited for high-power, high-frequency RF amplification due to its superior electron mobility?

Accepted Answer

GaAs MESFET

Answer

GaAs MESFETs leverage GaAs's high electron mobility (~8500 cm²/V·s vs. Si's ~1400) for superior high-frequency performance.

Question 2

The gain-bandwidth product (ft) of a BJT is determined by:

Accepted Answer

The transit frequency where current gain falls to unity

Answer

ft is the frequency at which the small-signal current gain magnitude falls to 1, characterizing the transistor's high-frequency limit.

Question 3

In a MOSFET, subthreshold conduction refers to:

Accepted Answer

Drain current flowing even when VGS < VT

Answer

Subthreshold current flows via diffusion even below VT and is characterized by the subthreshold slope (~60 mV/decade at room temperature).

Question 4

The depletion approximation in p-n junction analysis assumes:

Accepted Answer

The depletion region has abrupt boundaries with zero free carriers inside

Answer

The depletion approximation treats the depletion region as having abrupt edges with all mobile carriers absent, simplifying Poisson's equation.

Question 5

A thyristor (SCR) can be turned OFF by:

Accepted Answer

Reducing anode current below the holding current

Answer

Once latched, an SCR can only be turned off by reducing anode current below the holding current IH, not by gate control.

BEE - Bachelor of Electrical Engineering Practice Test