PN junctions and diodes

Why does a reverse current flow briefly (a reverse recovery time exists) when a PN junction diode is switched from forward to reverse?

  1. ABecause the metal electrode resistance is large
  2. BBecause minority carriers stored during forward conduction do not disappear immediately
  3. CBecause the package heats up
Show answer and explanation

Answer: B. Because minority carriers stored during forward conduction do not disappear immediately

During forward conduction, injected minority carriers are stored on both sides of the junction. After switching to reverse, current flows in the reverse direction until these carriers are swept out or recombine. This time is the reverse recovery time, which causes switching losses and noise.

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More PN junctions and diodes questions

  1. How does the built-in (diffusion) potential of a PN junction relate to the doping on each side?
  2. Which correctly describes the mechanism of avalanche breakdown?
  3. In a very heavily doped PN junction, what is the main mechanism of breakdown at low reverse voltage?
  4. What does a bridge rectifier made of four diodes do?
  5. How is a photodiode generally used to detect light?