Semiconductor Devices & Circuits Flashcards

What is the depletion region in a p-n junction?

Answer: The region devoid of mobile charge carriers near the junction

The depletion region forms at the p-n junction when electrons and holes recombine, leaving an area with no free charge carriers.

Which of the following describes the operation of an enhancement-mode NMOS transistor when VGS = 0?

Answer: Channel does not exist (OFF)

An enhancement-mode NMOS has no channel when VGS = 0; a positive gate voltage must exceed the threshold to create the channel.

The breakdown mechanism in heavily doped, thin-junction diodes at low reverse voltages is called:

Answer: Zener breakdown

Zener (or tunneling) breakdown occurs in heavily doped junctions where the strong electric field allows electrons to tunnel through the narrow barrier.

In a common-emitter amplifier, what is the phase relationship between the input and output signals?

Answer: 180° out-of-phase

The common-emitter configuration inverts the signal, producing a 180° phase shift between base input and collector output.

A varactor diode is used primarily as a:

Answer: Voltage-controlled capacitor

A varactor (varicap) diode's depletion-region width changes with reverse bias, varying its junction capacitance for tuning applications.

What is the pinch-off voltage in a JFET?

Answer: The gate-source voltage that reduces drain current to nearly zero

Pinch-off voltage (VP) is the gate-source voltage at which the depletion regions close the channel, reducing ID to approximately zero.

An SCR (Silicon Controlled Rectifier) can be triggered into conduction by:

Answer: Applying a positive pulse to the gate

An SCR latches ON when a positive gate trigger pulse fires it while the anode is positive with respect to the cathode.