Basic applications for Zener Diodes
Zener diodes are used most frequently in voltage-regulator applications. Here are a few applications.
Here, a zener diode is used to regulate the voltage supplied to a load. When Vin attempts to push Vout above the zener diode’s breakdown voltage (Vzener), the zener diode draws as much current through itself in the reverse-biased direction as is necessary to keep Vout at Vzener, even if the input voltage Vin varies considerably.
The value of the resistor can be found by using
where Imax, zener is the maximum current rating of the zener diode.The power rating of the resistor should be
are given by the formulas accompanying the figure.
This circuit shifts the input voltage (Vin) down by an amount equal to the breakdown voltage of the zener diode.
Two opposing zener diodes placed in series act to clip both halves of an input signal. Here, a sine wave is converted to a near squarewave. Besides acting as a signal reshaper, this arrangement also can be placed across apower supply’s output terminals to prevent voltage spikes from reaching a circuit that is attached to the power supply.The breakdown voltages of both diodes must be chosen according to the particular application.