Zener Diode & Its Applications

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Zener Diode & its Applications

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Zener Diode

• This is a diode designed with adequate power dissipation capabilities to operate in the breakdown region.

• When both sides are heavily doped, the depletion layer is very thin (100 Ǻ).

• Even 4 V may give a field of 107 V/m, causing breakdown.

• Whatever may be the breakdown phenomenon, it is called ‘zener diode’.

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Equivalent Circuits

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v By controlling the thickness of the depletion layer, Zener Diode can be made to have breakdown at a specified Zener Voltage.

v Generally Zener Voltage ranges from 0 volts to 200 volts.

v As long as the current through the diode is limited by the external resistance in the circuit within permissible values, it does not burn out.

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Zener Diode Applications

1. Voltage Stabilizer or Regulator.2. Peak Clipper.3. Switching Operation.4. Reference Element.5. Meter Protection.

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Voltage Regulator

It has the ability to maintain a constant output even when either the input voltage or load varies.

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• A voltage regulator provides a constant voltage from a source whose voltage may vary appreciably.

Zener Diode 9 गु�वार, 11 फरवर�2010

Example

Zener Diode 11गु�वार, 11 फरवर�2010

• This voltage (82.5 V) is more than VZ (= 60 V).

• Hence, diode is ‘ON’.• Replace the diode by its equivalent.

This is more than VZ. Hence diode is ‘ON’. We now calculate the minimum value of zener current.

When V1 becomes 120 V :

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