Electronic Components and Devices Flashcards

Which parameter of a MOSFET is analogous to the transconductance of a BJT?

Answer: Transconductance (gm)

Transconductance (gm) relates the change in drain current to the change in gate-source voltage in a MOSFET.

A photodiode is operated in which mode for fastest response time?

Answer: Reverse bias (photoconductive mode)

Reverse bias (photoconductive mode) widens the depletion region, reducing junction capacitance and speeding up response.

What causes thermal runaway in a bipolar junction transistor?

Answer: Increased collector current raising junction temperature, further increasing current

Rising temperature increases leakage current, which raises collector current, generating more heat in a destructive positive feedback loop.

Which type of capacitor is NOT polarized and is commonly used in AC filtering applications?

Answer: Film (polyester)

Film capacitors are non-polarized and suitable for AC circuits, whereas electrolytic and tantalum types are polarized.

In an enhancement-mode N-channel MOSFET, current flows when the gate-source voltage (VGS) is:

Answer: Above threshold voltage

An enhancement-mode N-channel MOSFET requires VGS to exceed the threshold voltage to create the conducting channel.

What is the purpose of a bypass capacitor placed in parallel with the emitter resistor of a BJT amplifier?

Answer: Bypass AC signal to increase AC gain

A bypass capacitor short-circuits the emitter resistor at AC frequencies, eliminating the gain-reducing negative feedback.

Which device is best described as a voltage-controlled variable resistor operating in its ohmic region?

Answer: MOSFET in ohmic (linear) region

A MOSFET biased in its ohmic (linear) region acts as a voltage-controlled resistor, with RDS controlled by VGS.