ISCET Semiconductor Device Principles 3

Question 1

What is the diffusion capacitance of a forward-biased p-n junction proportional to?

Accepted Answer

Forward bias current

Answer

Diffusion capacitance is proportional to the DC forward bias current because more current means more stored minority charge.

Question 2

In an enhancement-mode N-channel MOSFET, the device is normally:

Accepted Answer

OFF with zero gate bias and turned ON by positive VGS above threshold

Answer

Enhancement-mode MOSFETs have no channel at VGS = 0 and require VGS > VTH to invert the channel and allow drain current.

Question 3

What is the transconductance (gm) of a MOSFET in the saturation region given ID = 4 mA and VGS – VTH = 2 V?

Accepted Answer

4 mA/V

Answer

In saturation, gm = 2·ID / (VGS – VTH) = (2 × 4 mA) / 2 V = 4 mA/V.

Question 4

Which type of breakdown in a reverse-biased diode is dominant at voltages below approximately 5 V in heavily doped junctions?

Accepted Answer

Zener (tunneling) breakdown

Answer

Zener (band-to-band tunneling) breakdown dominates in heavily doped junctions at low reverse voltages (below ~5 V) where the depletion region is very narrow.

Question 5

The pinch-off voltage (VP) of a JFET is the value of VGS at which:

Accepted Answer

The channel is completely depleted and drain current drops to zero

Answer

Pinch-off voltage is the gate-to-source voltage that fully depletes the channel, cutting off drain current (IDSS approaches zero).

(ISCET) International Society of Certified Electronics Technicians Practice Test

(ISCET) International Society of Certified Electronics Technicians Practice Test

ISCET Semiconductor Device Principles 3