Question: Q. 4. A zener diode is fabricated by heavily doping both and sides of the junction. Explain, why? Briefly explain the use of zener diode as a voltage regulator with the help of a circuit diagram.
U] [Delhi II 2017]
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Solution:
Ans. Explanation of heavily doping of both and sides of Zener diode.
Circuit diagram of Zener diode as a dc voltage regulator.
1
Explanation of the use of Zener diode as a voltage regulator.
By heavily doping both and sides of the junction, depletion region formed is very thin, i.e., . Hence, electric field, across the junction is very high even for a small reverse bias voltage. This can lead to a ‘breakdown’ during reverse biasing.
If the input voltage increases/decreases, current through resister , and Zener diode, also increases/decreases. This increases/decreases the voltage drop across without any change in voltage across the Zener diode.
This is because, in the breakbown region, Zener voltage remains constant even though the current through the Zener diode changes.
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