1 Zener Diode Tutorial

Ordinary diode allows current to flow in one direction only, zener diode on the other hand allows the current to flow on both direction. When the zener is forward bias, the voltage drop across is around 0.7V, which is equal to the ordinary diode. But if the zener is reverse bias, it has a voltage drop equal to its breakdown voltage, where in this case, ordinary diode is open circuit or not conducting.

zener diode symbol

One of the uses of this diode is for voltage regulation or voltage reference. The figure below is an example on how the zener diode provides regulation  across the load. the voltage output is equal to the zener diode voltage.

Example:

V_input = 15V

Zener = 10V

R = 500 ohm

Load = 2000 ohm

we can say that the current delivered to the load is equal to Vload/Iload
where Vload = Vzener = 10V, thus current of load = 5mA

voltage regulation

Zener can be connected in series to each other or connected back to back depending on its purpose. Series connection (see circuit below), provides different voltage reference or output with one input only. Example the input voltage is 35V, you can have an output of 25V and 10V connecting 25v and 10V zener in series.

series connection

Zener diode also can be connected back to back to provide voltage regulation especially in square wave or sine wave signal input. Example a sinusoidal wave has a magnitude of 50V at 60Hz (see circuit below), the two zener diodes connected back to back provides a regulated output of  with the maximum magnitude of output equal to +15V and -15V.See the output voltage (faded blue) and input voltage in diagram below.

back to back connection

back to back zener output voltage

Sample project that uses zener diode as regulator

1. 12V to 6V DC converter using Zener diode and transistor
2. other regulator