BEE Semiconductor Devices and Circuits 3

Question 1

In a full-wave bridge rectifier with a transformer secondary voltage of 12 Vrms and ideal diodes, what is the average DC output voltage?

Accepted Answer

10.8 V

Answer

Vpeak = 12√2 ≈ 16.97 V; Vavg = (2/π)Vpeak ≈ 0.637 × 16.97 ≈ 10.8 V.

Question 2

The transconductance gm of a MOSFET in saturation is proportional to which of the following?

Accepted Answer

(VGS − VT)

Answer

In saturation gm = ∂ID/∂VGS = kn(VGS − VT), so gm is proportional to (VGS − VT).

Question 3

Which parameter of a BJT is defined as the ratio of collector current to base current?

Accepted Answer

β (beta)

Answer

β (hFE) = IC/IB is the common-emitter current gain of a BJT.

Question 4

A CMOS inverter draws maximum power during which condition?

Accepted Answer

During input signal transitions

Answer

CMOS draws significant current only during transitions when both transistors are momentarily on, dissipating dynamic power.

Question 5

In a p-n junction, the diffusion capacitance is dominant under which bias condition?

Accepted Answer

Moderate to strong forward bias

Answer

Diffusion (storage) capacitance arises from minority carrier charge stored during forward bias and dominates in forward-biased junctions.

BEE - Bachelor of Electrical Engineering Practice Test