Why is a Zener diode used to keep a voltage steady (as a regulator)?
A Zener diode is designed to operate in reverse breakdown, where its voltage stays almost constant over a wide range of current.
A Zener diode is designed to operate in reverse breakdown, where its voltage stays almost constant over a wide range of current. Connected in reverse across a load, it soaks up variations: if the supply rises, the Zener draws more current but the voltage across it — and the load — barely changes. So it 'pins' the output to the Zener voltage, regulating it.
Key point
In reverse breakdown a Zener holds a nearly constant voltage, so it regulates.
Common mistake
thinking the Zener is damaged when it works in breakdown.
Memory tip
Zener lives in reverse breakdown on purpose — constant-voltage clamp.
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