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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 ...
Thus, as long as the Zener current (I Z) is above a certain level (called holding current), the voltage across the Zener diode (V Z) will be constant. Resistor, R1, supplies the Zener current and the base current (I B) of NPN transistor (Q1). The constant Zener voltage is applied across the base of Q1 and emitter resistor, R2.
Selenium diode:Depends on age and current. Usually higher than silicon diodes. Silicon diode: cutoff occurs when Vf falls below apx 0.7 V. The exact voltage varies with temperature. Thermionic diode: cutoff voltage depends on device design. Much higher than for silicon devices. Zener diode: reverse cutoff defined by diode voltage rating ...
The diode, a nonlinear device, is in series with a linear circuit consisting of a resistor, R and a voltage source, V DD. The characteristic curve (curved line), representing the current I through the diode for any given voltage across the diode V D, is an exponential curve.
When input voltage rises, the diode dumps current to maintain the set output voltage. This kind of regulator is usually employed only in low voltage, low current circuits because Zener diodes have both voltage and current limitations. It is also very inefficient, because it dumps excess current, which is not available to the load.
Zener diode based noise source. A noise generator is a circuit that produces electrical noise (i.e., a random signal). Noise generators are used to test signals for measuring noise figure, frequency response, and other parameters. Noise generators are also used for generating random numbers. [1]
Diode I-V diagram. Breakdown voltage is a parameter of a diode that defines the largest reverse voltage that can be applied without causing an exponential increase in the leakage current in the diode. Exceeding the breakdown voltage of a diode, per se, is not destructive; although, exceeding its current capacity will be.