Govt. Exams
Entrance Exams
Voltage divider bias with emitter resistor provides stability and increases input impedance through negative feedback from emitter resistor.
Low doping leads to wide depletion region favoring avalanche breakdown (impact ionization) rather than direct Zener tunneling.
Schottky diodes have forward voltage ~0.3-0.4V (vs 0.7V for Si) and fast switching due to no stored charge in depletion region.
As load current increases, less current flows through the Zener diode to maintain constant output voltage, so Zener current decreases.
Early voltage (VA) is a parameter that depends on the base width modulation effect with collector-base reverse bias voltage.
In triode region, the condition VDS < VGS - VTh allows the channel to conduct with resistance proportional to VDS.
Holding current IH: minimum anode current to sustain regenerative action (latching); if IA < IH, device reverts to blocking state.
Photodiode: Iph = η·q·Φ where η is quantum efficiency and Φ is incident photon flux; reverse bias increases depletion width for carrier collection.
CLM: as VDS increases, pinch-off point moves toward source, reducing effective channel length; output resistance Rds = VA/ID = λ⁻¹.
GBW ≈ fT; BJT current gain drops with frequency as β·f ≈ constant, where fT is extrapolated cutoff frequency (~1GHz for silicon BJTs).
