BEE Semiconductor Devices and Electronics 3

Question 1

In a CMOS inverter, static power dissipation is nearly zero because:

Accepted Answer

Only one transistor conducts at a time in steady state

Answer

In steady state, either the PMOS or NMOS is OFF, creating no DC path from VDD to GND and eliminating static power.

Question 2

The built-in potential (contact potential) of a p-n junction at thermal equilibrium is caused by:

Accepted Answer

Diffusion of majority carriers and resulting charge separation

Answer

Diffusion of holes into the n-side and electrons into the p-side creates charge separation, establishing the built-in potential.

Question 3

Hall effect measurements in a semiconductor are used to determine:

Accepted Answer

Carrier concentration and carrier type

Answer

The Hall effect reveals carrier type (n or p) from the sign of the Hall voltage and carrier density from its magnitude.

Question 4

Which breakdown mechanism dominates in heavily doped p-n junctions at low reverse voltages?

Accepted Answer

Zener (tunneling) breakdown

Answer

Zener breakdown (band-to-band tunneling) occurs in heavily doped junctions with narrow depletion regions at voltages typically below 5 V.

Question 5

The transconductance of a BJT in the active region is given by gm =

Accepted Answer

IC / VT

Answer

For a BJT, gm = IC/VT where IC is collector current and VT = kT/q ≈ 26 mV at room temperature.

BEE - Bachelor of Electrical Engineering Practice Test