Definition
The Zener diode is a special type of diode that is designed to work in reverse bias and in the so-called Zener region of the diode characteristic curve. This region is after the reverse-biased voltage has exceeded the breakdown voltage (breakdown point)
Zener Diode Working Principle
If the reverse bias voltage is less than the breakdown voltage, or if the Zener diode is forward biased, it acts as an ordinary diode. That is, in forward bias it allows current, and in reverse bias it blocks current. After this voltage has surpassed the breakdown point (in reverse bias), the diode falls in the Zener region, where it conducts without getting damaged. Current in this region is called avalanche current. For a Zener diode, it is also called Zener current.
As soon as the voltage decreases, the diode retains its non-conducting condition and gets back to its normal properties. This specific property of being operational in the reverse bias and with avalanche current is given to the Zener diode by a rich doping of the semiconductor material.
Moreover, by controlling the amount of doping, the thickness of the depletion region in the PN junction and the breakdown voltage can be set to any value.
Applications of Zener Diode
1. Zener Diode as Voltage Regulator: Voltage regulator is a device which maintains constant output voltage without bothering about variation in input voltage and load current. Zener diode is used as the voltage regulator.
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| Zener Diode as Voltage Regulator |
The supply voltage Vs and the resistance Rs are so designed that the diode operates in breakdown region. Besides, Resistor Rs is used to limit the value of reverse current through the diode. The diode voltage Vz which is same as the voltage across the load RL is the zener voltage Vz.
Besides, the series resistor Rs absorbs the excess current to maintain constant output voltage. In this way, Zener diode maintains constant output voltage and eliminates the effect of voltage fluctuation and provide voltage regulation.
2. For Switching Operations: Zener diode is used as a switch. It is because of its ability to produce change from low current to high current. Thus, it is used as a switch.
3. As Clipper: Zener diode is used in wave shaping circuit as a clipper. It is used to clip input waveform in specific applications.
4. As a reference element: In various circuits reference elements are required for comparing voltages to a reference value.Thus, in such circuits, Zener diode is used as a reference element.
5. Meter protection: Zener diode is used in electronics circuit for the protection of multimeter. In some cases, excess current flows through a circuit and damage the multimeter. Thus, Zener diodes protect it from damage by providing voltage regulation.
Zener diode is significant to use in breakdown region. Due to its doping characteristics, the zener diode is made to use at high breakdown voltage.
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