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A Zener diode is a special type of diode designed to reliably allow current to flow "backwards" (inverted polarity) when a certain set reverse voltage, known as the Zener voltage, is reached. Zener diodes are manufactured with a great variety of Zener voltages and some are even variable.
In electronics, the Zener effect (employed most notably in the appropriately named Zener diode) is a type of electrical breakdown, discovered by Clarence Melvin Zener. It occurs in a reverse biased p-n diode when the electric field enables tunneling of electrons from the valence to the conduction band of a semiconductor , leading to numerous ...
The Zener effect is primarily exhibited by reverse-biased diodes and bipolar transistor base-emitter junctions that breakdown below about 7 volts. The breakdown is due to internal field emission, since the junctions are thin, and the electric field is high. Zener-type breakdown is shot noise.
In the Zener diode, the concept of PIV is not applicable. A Zener diode contains a heavily doped p–n junction allowing electrons to tunnel from the valence band of the p-type material to the conduction band of the n-type material, such that the reverse voltage is "clamped" to a known value (called the Zener voltage), and avalanche does not ...
Avalanche diodes (commonly encountered as high voltage Zener diodes) are constructed to break down at a uniform voltage and to avoid current crowding during breakdown. These diodes can indefinitely sustain a moderate level of current during breakdown. The voltage at which the breakdown occurs is called the breakdown voltage.
Three 1N4148 diodes in glass DO-35 axial package. The black band on the right is the cathode side. Diode schematic symbol vs cathode marking on the package. The 1N4148 is a standard silicon switching signal diode. It is one of the most popular and long-lived switching diodes because of its dependable specifications and low cost.
Voltage breakdown diodes are often used as noise generators. (Motchenbacher & Fitchen 1973, pp. 180–182) There are two breakdown mechanisms: Zener and avalanche. Diodes with the corresponding effects are known as Zener diodes and avalanche diodes. The two mechanisms have different noise behaviors.
A simple diode clipper can be made with a diode and a resistor. This will remove either the positive, or the negative half of the waveform depending on the direction the diode is connected. The simple circuit clips at zero voltage (or to be more precise, at the small forward voltage of the forward biased diode) but the clipping voltage can be ...