Semiconductor Devices Flashcards

What is the primary function of the depletion region in a reverse-biased PN junction?

Answer: To act as an insulating barrier that blocks majority carrier flow

The depletion region widens under reverse bias, creating an effective insulating barrier that prevents majority carriers from crossing the junction.

A Zener diode is operating in reverse breakdown at 6.2 V with 20 mA flowing through it. What is the power dissipated?

Answer: 0.124 W

Power = V × I = 6.2 V × 0.020 A = 0.124 W.

Which BJT configuration provides the highest voltage gain but has a current gain less than 1?

Answer: Common base

The common-base configuration has a current gain (alpha) slightly less than 1 but can provide significant voltage gain.

In an N-channel JFET, pinch-off voltage (Vp) is the gate-to-source voltage at which:

Answer: The channel is fully depleted and drain current drops to nearly zero

Pinch-off voltage is the negative VGS value that fully depletes the N-channel, reducing drain current (IDSS) to essentially zero.

Which parameter describes the ratio of the change in collector current to the change in base current in a BJT?

Answer: Beta (β)

Beta (β or hFE) is defined as IC/IB and represents the DC current gain of a BJT in common-emitter configuration.

A silicon diode has a forward voltage drop of approximately 0.7 V. If a germanium diode is used instead, the forward voltage drop would be approximately:

Answer: 0.3 V

Germanium diodes have a lower barrier potential of approximately 0.3 V compared to silicon's 0.7 V.

What is the effect of increasing temperature on the reverse saturation current (IS) of a PN junction diode?

Answer: IS increases, roughly doubling for every 10°C rise

Reverse saturation current approximately doubles for every 10°C temperature increase due to increased thermally generated minority carriers.