Semiconductor Devices and Electronics Flashcards

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

Answer: Only one transistor conducts at a time in steady state

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

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

Answer: Diffusion of majority carriers and resulting charge separation

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

Hall effect measurements in a semiconductor are used to determine:

Answer: Carrier concentration and carrier type

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

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

Answer: Zener (tunneling) breakdown

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

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

Answer: IC / VT

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

In an LED, light is emitted due to:

Answer: Radiative recombination of electron-hole pairs

In an LED, forward-biased minority carriers recombine radiatively, releasing photons with energy equal to the bandgap.

For an ideal op-amp, which of the following is true?

Answer: Infinite input impedance, zero output impedance, infinite open-loop gain

An ideal op-amp has infinite input impedance, zero output impedance, and infinite open-loop differential gain.