Zener diode

Zener-diode

a form of semiconductor diode in which at a critical reverse voltage a large reverse current can flow.

Zener diodes are made to conduct under reversed bias. Zener diodes are fabricated to work in the breakdown region under a special tunneling breakdown called Zener breakdown. This breakdown occurs at a specifically defined value of voltage, as this breakdown voltage is maintained as the reverse current increases, this diode can be used as a voltage reference. The breakdown voltage is kept constant even if the cur- rent changes without damaging the diode.

The main property of a zener diode is that the voltage across the diode ($V_Z$) will remain practically steady for a wide range of current ($I_Z$) when the diode is operated in reverse bias mode: