Zener Diode

ZENER DIODE

A zener diode is also called a voltage reference, voltage regulator (or) break down diode.

The zener diode is a silicon PN junction device which differs from a rectifier diode, in the sense, that it is operated in the reverse break down region.

The break down voltage of a zener-diode is set by controlling the doping level. The reverse break down of a PN junction may occur either due to avalanche (or) zener effect. At reverse voltage less than 6 volts, zener effect predominates, whereas above 6 volts avalanche effect is predominant.

Zener break down occurs due to breaking of covalent bonds by the strong electric field set up in the depletion region by the reverse voltage. It produces an extremely large number of electrons and holes which constitute the reverse saturation current. Whose value is limited only by the external resistance in the circuit. Avalanche break-down occurs at higher reverse voltages when thermally- generated electrons acquire sufficient energy to produce more carriers by collision.

Zener voltage:

Zener diode are available having zener voltages of 2.4 volts to 200 volts.

Zener Biasing:

For proper working of a zener diode in any circuit, it essential that it must be reverse biased and have voltage across it greater than Vz.

Application of zener diode:

(i) Voltage regulator

(ii) Used as peak clippers

(iii) For meter protection against damage from accidental application of excessive voltage.