In electronics terminology, when the diode’s anode is connected to the positive terminal and cathode to the negative terminal of a DC source, it is said to be connected in forward bias. A connection which is the other way round is called reverse bias. Zener diodes in forward bias behave like a normal diode. In reverse bias, they allow very little current to flow till the voltage across the diode reaches a predesigned value called Zener or breakdown voltage. On reaching this voltage, current flow increases, and the voltage drop across the diode remains constant for different current flows.
Specifications of these diodes
Zener diode is a unique kind of diode that is highly doped, has a specific value of breakdown voltage (Zener voltage) and the maximum power (Watts) it can dissipate. Commonly available Voltages range from 1 V to 63 V and Power rating from 200 mW to 5W. They are normally supplied as a set containing diodes of different voltages for a particular power rating. Zener diodes have a band around one end, showing the cathode side of the diode.
Used as a Voltage regulator
When constant output direct current voltage is needed under varying input voltage and or load current, Zener diode can be suitably used in the circuit to work as a voltage regulator. These diodes are connected parallel to the load and in reverse bias. Once the Zener diode exceeds Zener voltage, the voltage across the load will become constant.
As an Over-voltage protection
In a circuit when the input voltage is higher than Zener voltage, if the voltage across load resistance drops, there will be a short circuit. This situation can be avoided by connecting a Zener diode parallel to the load in reverse bias.
As a Reference Voltage
Circuits delivering fixed output voltage or a set of fixed output voltages can be made utilising a single Zener diode or by using many Zener diodes in series in combination with normal PN junction diodes. These fixed voltages can be used as reference voltages for calibration or in simulation work.
Clamping and Clipping circuits
Diode clipping and clamping circuits are circuits that are used to shape or modify an input AC waveform (or any sinusoidal waveform), producing a different shaped output waveform. They are mainly used for circuit protection as they can be designed to limit or clip-off the positive or negative part of an AC signal.
Categories Simillar to Zener Diodes includes LED Diodes, TVS Diodes and Varactor Diodes