Zener diodes are widely used as voltage references and as shunt controllers to adjust voltage across small circuits. When connected in parallel with a variable voltage source so it is inverse, a Zener diode leads when the voltage reaches the inverse voltage of the diodes.
The Zener diode is like a general signal diode. When tilted forward, it behaves like a normal signal diode, but when a reverse voltage is applied, the voltage stays constant for a wide range of currents. Avalanche Breakdown: There is a limit for reverse.
Zener diode operation is similar to a PN junction diode in front biased state, but the uniqueness is that it can also be done when it is connected in reverse over the threshold threshold / breakdown. These are among others the basic types of diodes commonly used, apart from normal diodes.
This mechanism is called high field emission or Zener breakdown. The value of the reverse voltage at which this occurs is controlled by the amount of diode doping. A highly doped diode has a low Zener voltage, while a light scattered diode has a high Zener noise.
Zener diodes can be used to produce a stabilized voltage output with a low discharge under varying load conditions. By passing a small current through a diode from a voltage source through a suitable current limiting resistor (RS), the zener diode will generate enough current to maintain a voltage drop of Vout.