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The Zener diode is
operated in reverse bias
mode (positive on its
cathode).
It relies on the reverse
breakdown voltage
occurring at a specified
value.
This value is printed on
it.
It has two main
applications.
1. as a reference
source, where the
voltage across it is
compared with another
voltage.
2. as a voltage
regulator, smoothing out
any voltages variations
occurring in the supply
voltage across the load.
When being used a
voltage regulator, if
the voltage across the
load tries to rise then
the Zener takes more
current.
The increase in current
through the resistor
causes an increase in
voltage dropped across
the resistor.
This increase in voltage
across the resistor
causes the voltage
across the load to
remain at its correct
value.
In a similar manner, if
the voltage across the
load tries to fall, then
the Zener takes less
current.
The current through the
resistor and the voltage
across the resistor both
fall.
The voltage across the
load remains at its
correct value.
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