Schottky diodes

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Schottky diodes,metal/semiconductor junction: this heterogeneous junction is characterized by the absence of storage of charges, it is therefore very fast. It is widely used in circuits fast logic (TTL Schottky).

Schottky diode symbol
Schottky diode symbol


A schottky diode works exactly the same as a diode.The differences are:

  • At the threshold voltage, which is no longer 0.7V, but 0.3V, at 0.4V
  • In terms of speed, schottky diodes are much faster and more expensive

Application:

  • Logic circuits: TTL LS technology and derivatives
  • Switching power supply

POWER SCHOTTKY DIODES:

  1. reduction of the voltage drop in the on state (0.4V at 1A/mm²).
  2. no reverse recovery phenomenon (therefore very fast diode) but appearance of a negative current of the same order of magnitude as the current of the fastest diodes.

only limitation: Reverse voltage withstand. it is difficult to exceed 200V

Varactor diode

varactor diode


This reverse biased diode behaves like a very low value capacitor, the capacity of which is variable according to the reverse voltage applied to its terminals.

Varicap diodes or varactor diodes are used in receiver tuning circuits to vary the resonant frequency of the tuning circuit by changing the control voltage applied to the diode.

Varactor diode applications

it has a characteristic of voltage controlled capacitance, they replaced the mechanically tuned capacitors.

Varactor diodes are used in televisions and radios operating at high frequencies. These find their application in

  • frequency multipliers.
  • bandpass filters.
  • amplifiers.




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