A Zener diode is a type of pn junction diode. Zener diodes are used in the breakdown region (yield region) by applying a voltage in the opposite direction to normal pn junction diodes.
Zener diode is a type of pn junction diode. Fig. 1 shows the V–I curve of the pn junction diode. Typical pn junction diodes are used with a forward bias whereas Zener diodes are used with a reverse bias as they are designed to operate in the breakdown region. There are the following two breakdown mechanisms depending on the dopant concentration of the p-type and n-type semiconductors. Since both breakdown events occur at a fixed voltage when temperature is constant, Zener diodes are also called voltage regulator diodes and constant-voltage diodes.
In practice, there are no distinct regions in which these breakdown events occur. Zener breakdown is more dominant below 6 V whereas avalanche breakdown is more dominant above 6 V.
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