Zener Diode

  1. It is a specially designed diode which is optimized to operate in breakdown region.
  2. Zener diode is silicon diode.
  3. By varying the doping level silicon diode, a manufacturer can produce zener diodes with breakdown voltage from about 2 to 200V.

Applications of Zener Diodes

  • As voltage stabiliser
  • For meter protection
  • For wave shaping

Varactor Diodes

  1. Varactor diode operates under reverse biased conditions.
  2. Varactors are silicon diodes optimized for their variable capacitance.
  3. These diodes are voltage controlled diode.
  4. These diodes are used in television receiver, FM receivers, automobile radios and other communication equipment.

Light Emitting Diodes (LEDs)

  1. These are made from gallium arsenide phosphide (GaAsP) and Gallium phosphide (GaP).
  2. LEDs have a typical voltage from 1.5V to 2.5V for currents between 10mA to 50mA.
  3. LEDs have longer life, more than 20 years.
  4. They use in panel indicators, digital watches, calculators, multimeters, intercoms etc.

Photo Diodes

  1. It is also known as photodectector.
  2. Photodiode is optimized for its sensitivity to light.
  3. Photo diode operates under reverse biased conditions.

Schottky Diode

  1. Schottky diode is a special purpose diode.
  2. For its construction, a metal like gold, silver or platinum is used on one side of the junction and doped silicon is used on the other side.
  3. Schottky diode can easily rectify signals of frequency above 300MHz without distortion.
  4. These diodes are best suited for low voltage rectification.
  5. Schottky diodes find their best application in these computers because of their fast operation.
  6. These diodes are also used for rectification of high frequency (50MHz to 500MHz) signals such as in digital computers.

Tunnel Diodes

  1. By increasing the doping level, we can get breakdown at 0V, such diodes are known as tunnel diodes.
  2. This diode has negative-resistance region.
  3. The tunnel diode is useful in high-frequency oscillatory circuits.