PN junctions and diodes

What is the forward voltage (the approximate voltage at which current starts to flow) of a typical silicon PN junction diode?

  1. AAbout 3 V
  2. BAbout 0.1 V
  3. CAbout 0.6–0.7 V
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Answer: C. About 0.6–0.7 V

A silicon diode starts conducting significant current when the forward voltage exceeds about 0.6–0.7 V. This value is related to the band gap and varies with material and structure: about 0.2–0.4 V for Schottky barrier diodes and about 3 V for GaN-based blue LEDs.

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More PN junctions and diodes questions

  1. How does the reverse saturation current of a PN junction diode depend on temperature?
  2. Which is a characteristic of a Schottky barrier diode?
  3. Which property does a variable-capacitance (varactor) diode use?
  4. In a PN junction where the p side is far more heavily doped than the n side (a p+n junction), how does the depletion layer spread?
  5. Why does a reverse current flow briefly (a reverse recovery time exists) when a PN junction diode is switched from forward to reverse?