THE ZENER DIODE

Zener diodes - Its a p-n junction diode in which runs in reverse bias condition when the voltage reaches the breakdown point. A stable voltage can be achieved by placing a resistor across it to limit the current.                                                   This diode is used to provide reference voltage in power supply circuits.These Diodes are specifically intended to make use of one or other of these break down(avalanche or zener breakdown) effect.                                                                                                                                                  When a zener diode is used it is operated at a reverse bias voltage which is slightly higher than its breakdown voltage.Under this condition the voltage across the diode is very nearly independent of the current through it.                                                                                                                       ZENER BREAKDOWN.This is the result of the electric field across the depletion layer becoming high enough to tear electron away from their nuclei and so produce a large number of electron hole pair.This has very marked effect on the number of minority carriers present and lead to massive increase in the reverse current.                   AVALANCHE BREAKDOWN.This it occur in diodes which have low level of doping.