| Cue (Question) | Notes (Answer) |
|---|---|
| How does a depletion region form? | Majority carriers diffuse; electrons and holes recombine near junction; immobile ions remain; net charge creates internal electric field from n→p |
| Direction of internal electric field? | From n-side (positive ions) to p-side (negative ions) |
| What is reverse saturation current? | Very small current in reverse bias due to minority carriers; increases dramatically at breakdown |
| What happens at reverse breakdown? | Sharp increase in current at high reverse voltage; Zener breakdown (heavy doping) or avalanche breakdown (high voltage) |
| Half-wave rectifier: what cycles conduct? | Only positive half-cycle (one diode conducts); output frequency = input frequency f |
| Full-wave rectifier types? | Center-tapped (2 diodes) or Bridge rectifier (4 diodes in H-bridge); output frequency = 2f |
| Which rectifier is more efficient? | Full-wave rectifier — uses both half-cycles; higher average output voltage |
| What is ripple factor? | Ratio of RMS AC component to DC component in rectifier output; lower = better |
Summary: The p-n junction depletion region arises from carrier diffusion and is maintained by the internal electric field opposing further diffusion. Forward bias narrows it; reverse bias widens it. Rectifiers exploit the diode's one-way conduction to convert AC to pulsating DC. Full-wave rectifiers are more efficient and produce double the frequency output compared to half-wave.