ISCET Semiconductor Devices 3

Question 1

In a MOSFET, the gate terminal is insulated from the channel by which material?

Accepted Answer

Silicon dioxide (SiO2)

Answer

The MOSFET gate is separated from the channel by a thin silicon dioxide (SiO2) insulating layer, which is why virtually no gate current flows.

Question 2

A BJT is said to be in saturation when:

Accepted Answer

Both the base-emitter and base-collector junctions are forward biased

Answer

Saturation occurs when both junctions are forward biased, causing VCE to drop to a low value (typically 0.2 V for silicon) and the transistor acts like a closed switch.

Question 3

What is the primary advantage of a Darlington pair transistor configuration?

Accepted Answer

Very high current gain (β² ≈ β1 × β2)

Answer

A Darlington pair cascades two BJTs so their betas multiply, yielding an extremely high overall current gain equal to approximately β1 × β2.

Question 4

Which type of diode is specifically designed to emit light when forward biased?

Accepted Answer

Light-emitting diode (LED)

Answer

LEDs are made from direct-bandgap semiconductors (like GaAs or GaN) where electron-hole recombination releases energy as photons rather than heat.

Question 5

The Early effect in a BJT refers to:

Accepted Answer

Narrowing of the base width as VCE increases, causing IC to rise slightly

Answer

The Early effect (base-width modulation) occurs when higher VCE widens the collector depletion region, effectively narrowing the base and slightly increasing IC.

(ISCET) International Society of Certified Electronics Technicians Practice Test

(ISCET) International Society of Certified Electronics Technicians Practice Test

ISCET Semiconductor Devices 3