Page 28 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

Fig 7

Zener diode: This diode specially designed for voltage regulation. A wide range of voltage regulated zener diodes
are available.
It is a PN junction diode doped heavily for regulation purpose. It has a normal VI characteristic when it is forward
biased. But the characteristic are changed abruptly when it is connected in reverse bias.
In the reverse bias condition a leakage current in the order of Microamps will flow. When the reverse voltage
reaches to a particular designed voltage a sudden breakdown known as avalanche breakdown happens.

When a heavy current flows at constant voltage, the voltage continue to remain constant. Further increase in
voltage, the current suddenly increases. Fig 8 shows the reverse characterises of zener diode.

Fig 8

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CITS : Power - Electrician & Wireman - Lesson 60-69