Practical Electronics/Diodes

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Diodes are semiconductor devices that allow electricity to flow through them in only one direction.

Types of diode:

  • Electrolytic - obsolete wet chemical diodes used in the 1920s
  • Copper oxide - poor efficiency, high leakage current. Obsolete
  • Thermionic diode - aka vacuum tube, valve. Obsolete.
  • Selenium - ditto. Terrible stink when they fail
  • Germanium diode - very low voltage drop, often used as a radio detector
  • Silicon diode - by far the most popular type. 0.6v knee, with Vf rising to typically 0.9-1.5v at I_max, but sometimes higher.
  • Schottky diode - lower Vf, much used in SMPSUs for greater energy efficiency
  • Ultrafast diode - quick recovery diode, maintains high efficiency at high frequency
  • Varicap diode - capacitance varies with applied reverse voltage. Mainly used as tuning capacitors
  • Zener diode - conduct at a specified Vr, used mainly for voltage regulation
  • Light emitting diode - used for lighting