Question

Explain the working of Zener diode and mention its applications.

Answer 1

Symbol of Zener Diode

 

 We can identify the terminals of zener diode by observing a black color ring at cathode terminal (refer the first figure in this post). If it is a SMD component, then a band will be available for cathode terminal.  A Zener diode is a silicon semiconductor device that permits current to flow in either a forward or reverse direction. The diode consists of a special, heavily doped p-n junction, designed to conduct in the reverse direction when a certain specified voltage is reached.  The Zener diode has a well-defined reverse-breakdown voltage, at which it starts conducting current, and continues operating continuously in the reverse-bias mode without getting damaged. Additionally, the voltage drop across the diode remains constant over a wide range of voltages, a feature that makes Zener diodes suitable for use in voltage regulation.

Operation of Zener Diode:

 Zener diodes are normally used only in the reverse bias direction.

 It means that the anode must be connected to the negative side of the voltage source and the cathode must be connected to the positive side.

 A main difference between zener diodes and regular silicon diodes is the way they are used in the circuits.

 It is primarily used to regulate the circuit voltage as it has constant VZ. 

 A large change in IR will cause only a small change in VZ. It means that a zener diode can be used as an alternate current path. The constant VZ developed across the diode can then be applied to a load. 

 Thus the load voltage remains at constant by altering the current flow through the zener diode.

Zener diode applications: Zener diodes are used for voltage regulation, as reference elements, surge suppressors, and in switching applications and clipper circuits.