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ZENER DIODE

1. WHAT IS ZENER DIODE?

=> structurally Zener diode is just a heavily doped P-N junction diode. but is varies form a P-N junction by a lot in working and use. (stating that Zener diode is just heavily doped p-n junction diode is the same as stating that vodka is just rotten potato).

2. HOW IS A ZENER DIODE DIFFERENT FROM A P-N JUNCTION DIODE?

  1. Zener diode is much heavily doped than a norman junction diode. so the concentration of free charge carriers is much higher.
  2. the depletion layer of the Zener diode is much thinner than the p-n junction diode.
  3. breakdown voltage is much lower and sharp than p-n junction diode,
  4. it works in reverse bias by Zener effect (explained below) whereas p-n junction diode works by avalanche effect.

3. WORKING OF ZENER DIODE

1. in forward biasing, the Zener diode works in the same way as the p-n junction diode.

2. in reverse biasing...

-the breakdown voltage of the Zener diode is much lower than that of P-N junction diode

-much sharp increase in current occurs at the breakdown in Zener diode

-the crystal structure of the diode is not damaged due to heating at breakdown because the Zener effect is reversible.

4. ZENER BREAKDOWN / Zener effect

=>  we know, that there is an electric field set up across the depletion layer.  the electric field is very large for the same voltage in Zener diode because of the high concentration of immobile charges.

=>we also know reverse biasing increases the depletion layer and thus the electric field across it. so for same voltage applied, the increase in the electric field is increased enormously in Zener diode.

=> the excessive electric field breaks the covalent bond between atoms in the depletion layer and creates free charge carriers. thus, a large number of charge carriers are created and a sharp current flows through the diode.


5. Difference between Zener effect and the avalanche effect.

ZENER EFFECTAVALANCHE EFFECT
1. Free charge carriers are created by breaking of covalent bond in the depletion region.1. Free charge carriers are created by breaking of covalent bond not in the depletion region.
2. bonds are broken due to strong electric field
2. bonds are broken due to fast-moving electrons
3. much heating doesn't occur and the diode is not damaged.
3. much heating occur and diode may be damaged.
4. responsible for conduction of zener diode in reverse biasing
4. responsible for conduction of p-n junction diode in reverse biasing