Zener Diode

Zener diode is a heavily doped p-n junction diode, which operates in reverse breakdown region.

Zener diodes are fabricated with precise breakdown voltages,which are controlled by its doping level during maufacturing.

Which is invented by physicist Carl zener.

Generally break down voltages ranging from 3 V to 200V. 

image 1:Zener diode symbol