A Zener diode is a special type of diode that is designed to allow current to flow "backwards" when a certain set reverse voltage, known as the Zener voltage, is reached. Zener diodes are manufactured with a wide range of Zener voltages and are widely used as voltage references and as shunt regulators to regulate the voltage across small circuits. Here are some key features of Zener diodes:
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A Zener diode exhibits almost the same properties as a regular diode, except the device is specially designed so as to have a reduced breakdown voltage, the so-called Zener voltage.
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By contrast with the conventional device, a reverse-biased Zener diode exhibits a controlled breakdown and allows the current to keep the voltage across the Zener diode close to the Zener breakdown voltage.
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The Zener diodes operation depends on the heavy doping of its p–n junction. The depletion region formed in the diode is very thin (<1 µm) and the electric field is consequently very high (about 500 kV/m) even for a small reverse bias voltage of about 5 V, allowing electrons to tunnel from the valence band of the p-type material to the conduction band of the n-type material.
Zener diodes are commonly used in electronic circuits as voltage regulators, voltage references, and shunt regulators. They are also used in power supplies to regulate voltage by acting as complementary loads, drawing more or less current as necessary to ensure a constant voltage drop across the load.
