how does a zener diode work?

Answer 1

Zener diodes work like other diodes by using a doped p-n junction. What's special about the Zener diode is the p-type material is heavily doped allowing a controlled amount of electrons to "tunnel" across. This means that the Zener diode, unlike other diodes is extremely stable in its reverse breakdown state. Note as stated in an earlier answer, the current although stable, is quite low and so the Zener diode is best used as an accurate voltage reference, not as a current source.

Answer 2

A Zener diode is a type of diode that permits current to flow in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than the rated breakdown voltage known as "Zener knee voltage" or "Zener voltage".

A conventional solid-state diode will not let significant current flow if reverse-biased below its reverse breakdown voltage. By exceeding the reverse bias breakdown voltage, a conventional diode is subject to high current flow due to avalanche breakdown. Unless this current is limited by external circuitry, the diode will be permanently damaged. In case of large forward bias (current flow in the direction of the arrow), the diode exhibits a voltage drop due to its junction built-in voltage and internal resistance. The amount of the voltage drop depends on the semiconductor material and the doping concentrations.

A Zener diode exhibits almost the same properties, except the device is especially designed so as to have a greatly reduced breakdown voltage, the so-called Zener voltage. 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. A reverse-biased Zener diode will exhibit a controlled breakdown and let the current flow to keep the voltage across the Zener diode at the Zener voltage. For example, a diode with a Zener breakdown voltage of 3.2 V will exhibit a voltage drop of 3.2 V if reverse biased. However, the current is not unlimited, so the Zener diode is typically used to generate a reference voltage for an amplifier stage, or as a voltage stabilizer for low-current applications.

The breakdown voltage can be controlled quite accurately in the doping process. Tolerances to within 0.05% are available though the most widely used tolerances are 5% and 10%.

The effect was discovered by the American physicist Clarence Melvin Zener.

Another mechanism that produces a similar effect is the avalanche effect as in the avalanche diode. The two types of diode are in fact constructed the same way and both effects are present in diodes of this type. In silicon diodes up to about 5.6 volts, the zener effect is the predominant effect and shows a marked negative temperature coefficient. Above 5.6 volts, the avalanche effect becomes predominant and exhibits a positive temperature coefficient.

In a 5.6 V diode, the two effects occur together and their temperature coefficients neatly cancel each other out, thus the 5.6 V diode is the part of choice in temperature critical applications.

Modern manufacturing techniques have produced devices with voltages lower than 5.6 V with negligible temperature coefficients, but as higher voltage devices are encountered, the temperature coefficient rises dramatically. A 75 V diode has 10 times the coefficient of a 12 V diode.

All such diodes, regardless of breakdown voltage, are usually marketed under the umbrella term of 'zener diode'.

Answer 3

A Zener diode is a junction diode that's designed to have a particular opposite breakdown voltage. The forward conduction V-I characteristics are comparable between a Zener diode and a familiar PN junction diode. The opposite bias characteristics are diverse: A PN junction diode is designed to have a extremely severe opposite breakdown voltage mutually as a Zener diode is designed to have a particular breakdown voltage interior of a extremely narrow band of values for a given form. Zener diodes will function in opposite bias mode as lengthy because of the fact the finished means dissipation does not exceed the gadget score. a familiar PN diode should not be used for this utility because of the fact the better opposite bias required to realize conduction isn't predictable, and could deliver approximately larger gadget means dissipation because of the better voltage, and the diode may be concern to avalanche breakdown destroying the PN junction.

Answer 4

Zener diode is just like a normal diode with one exception, they are heavily doped, and they are made such a way so that can dissipation large amount of heat and don't get destroyed even when high current pass through them. Also depletion area of such is relatively thin and thereby its breakdown voltage is can be quite specific.

They are normally used in "reverse" biased in series with a resistor when they should not be conductive because of the reverse bias. But even in reverse bias if you increase the voltage (i,e electric field) in a diode about a certain threshold then the electrons at such high voltage ( i,e in electric field) gains lots of energy and knocks out more electron from lattice by collision and thereby create a huge flow of excess or avalanche of electron- a process called "Avalanche Breakdown". Remember this so called "breakdown" leads to generation of large amount of heat, and thereby temp leads to the irreversible damage in case of a normal diode. While a Zener diode can whistand the surge of current and not get damaged. This Avalanche effects primarily happens in a lightly doped diode (with depletion area that is relatively long). But Zenner diode is a heavily doped diode and its depletion area is relatively thin, so that most of the electrons cannot accelerate enough through this thin depletion area, rather most of the electrons tunnel (a quantum mechanical process) through this heavily doped thin junction and create huge electron surge, a process called Zener breakdown. In a practical Zenner diode either or both the process (Avalanche or Zener) can be present.

Such processes leads to the huge increase of current through the zener diode but at the same time the resistance of the zenner diode itself decrease, but such increase of current and decrease of resistance are proportional so such that the product Uout=(current)x(zenner resistance) remains constant. So if Uin increase or decrease, the zenner makes it sure that the current through the zenner increase or decrease (while resistance of the zenner decrease or increase) but always the product = current x resiatance= Uout=voltage drop across zenner remains constant.

So you get a constant or regulated voltage(Uout) from a varying or unregulated DC voltage(Uin) and such regulation is maintained automatically.

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Answer 5

zener diode is a reverse biased diode in which p and n type semiconductor are highly dopped

Answer 6

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