# working of zener diode in AC in reverse bias

Discussion in 'General Electronics Chat' started by gladinaveen, Aug 9, 2008.

Aug 9, 2008
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can anybody say what happens when the zenerdiode is connected in reverse bias with AC SUPPLY

2. ### sudharshan.panduranga Active Member

Apr 10, 2008
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The Zenerdiode start to conduct after it reaches zener breakdown voltage.

Eg:
If u apply 10V AC to the zener of 5.1V value, it start 2 conduct when I/P voltage is increased beyond 5.1V. The load follow the I/P.

3. ### Wendy Moderator

Mar 24, 2008
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A zener acts much like a regular diode, until the breakdown voltage is reached. You would get something that vaugly resembles a square wave.

4. ### munna007 Active Member

Jul 23, 2008
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i think zener diode behaves normally under forward voltage n breaksdown at its breakdownlimit ...n then constant current starts flowing through it......under reverse bias it will not damaged .....current
flow after it s breakdown....

5. ### Wendy Moderator

Mar 24, 2008
21,825
3,039
No. It is not constant current. It is a relatively constant voltage, which is why zener diodes are used for voltage references. Once it is back biased to it's breakdown voltage (zener voltage) it conducts just enough to keep the same voltage across it, reguardless of current. You can burn them out by having too much current flowing through them, as they dissapate power like a resistor (P(watts) = V (zener voltage) * Current). All zener diodes have a wattage rating for this reason.

6. ### nanovate Distinguished Member

May 7, 2007
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Their voltage in either direction is not constant either (but varies much much less than the current so it is called constant).

This is true for "regular" didoes also -- what damages them is if you exceed their rated power.