Semiconductor Devices and Circuits Flashcards
7 cards from real BEE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Semiconductor Devices and Circuits flashcards as text
In a differential amplifier with a tail current source ITAIL, increasing ITAIL primarily affects which parameter?
Answer: Transconductance gm and thus differential gain
Each transistor's bias current is ITAIL/2, so increasing ITAIL raises gm = IC/VT and therefore increases the differential voltage gain.
The Miller effect in an inverting amplifier stage causes the input capacitance to appear as:
Answer: Cgd × (1 + |Av|)
By Miller's theorem, a feedback capacitance Cgd appears at the input multiplied by (1 + |Av|), significantly increasing effective input capacitance.
What type of semiconductor material results when silicon is doped with phosphorus?
Answer: n-type, with electrons as majority carriers
Phosphorus has five valence electrons; donating one to the lattice creates a free electron, making the silicon n-type.
In a cascode amplifier topology, placing a common-gate (or common-base) stage above a common-source (or common-emitter) stage primarily provides:
Answer: Increased output resistance and reduced Miller effect for wider bandwidth
The cascode's common-gate stage shields the input transistor from drain voltage swings, suppressing the Miller effect and raising output resistance, extending bandwidth.
A tunnel diode exhibits negative differential resistance (NDR) because of which quantum mechanical phenomenon?
Answer: Quantum tunneling of carriers through a very thin junction barrier
In heavily doped tunnel diodes, electrons quantum-mechanically tunnel through the thin junction, producing a current peak followed by an NDR region.
For a PMOS transistor to operate in the saturation region, which condition must be satisfied?
Answer: VSD ≥ VSG − |VTP|
For a PMOS in saturation, VSD ≥ VSG − |VTP|, which ensures the channel is pinched off at the drain end.
The transit frequency fT of a BJT is defined as the frequency at which the common-emitter current gain β drops to:
Answer: Unity (1)
The transit frequency fT is defined as the frequency where the magnitude of the common-emitter short-circuit current gain equals 1.