Zener diodes are a unique type of diode which permits current to flow in the forward direction and also allows current to flow in the reverse direction when the voltage is above
a certain value. This breakdown voltage is known as the Zener voltage (VZ). In non-Zener diodes, the Zener voltage is high, and the diode becomes permanently damaged if a reverse
current above ZV is allowed to pass through it. Zener diodes are designed so that the ZV is at a much lower value which allows a controlled breakdown which does not damage the diode
when a reverse current above the Zener voltage passes through.
Zener diodes are often used in voltage stabilizers/regulators, surge suppressors, peak clippers, switching operations, reference elements and in many other applications. The constant
reverse voltage of a Zener diode renders it a very useful component in regulating the output voltage against variations in the load resistance or variations in the input voltage from
an unregulated power supply. The current through the Zener diode will change (regulate) in order to keep the voltage within the threshold limits of Zener action and the maximum power
that it can dissipate.