# Zener Diode – Explanation, Specifications, Applications, Circuit Symbol

• Last Updated : 26 Sep, 2021

A semiconductor material has an electrical conductivity value falling between that of a conductor, such as metallic copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways by introducing impurities (doping) into the crystal structure. When two differently doped regions exist in the same crystal, a semiconductor junction is created. The behaviour of charge carriers, which include electrons, ions and electron holes, at these junctions is the basis of diodes, transistors and most modern electronics.

Some examples of semiconductors are silicon, germanium, gallium arsenide, and elements near the so-called metalloid staircase on the periodic table. After silicon, gallium arsenide is the second-most common semiconductor and is used in laser diodes, solar cells, microwave-frequency integrated circuits, and others. Silicon is a critical element for fabricating most electronic circuits. This article is about Zener diode before that we have a glance at related topics.

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### p-n Junction

A p-n junction is an interface or a boundary between two semiconductor material types, namely the p-type and the n-type, inside a semiconductor.

The p-side or the positive side of the semiconductor has an excess of holes and the n-side or the negative side has an excess of electrons. In a semiconductor, the p-n junction is created by the method of doping

Formation of p-n Junction

• We utilize distinctive semiconductor materials to make a p-n intersection, there will be a grain limit that would restrain the development of electrons from one side to the next by dispersing the electrons and openings and accordingly, we utilize the method involved with doping.
• We will comprehend the most common way of doping with the assistance of this model. Allow us to consider a meagre p-type silicon semiconductor sheet.
• On the off chance that we add a modest quantity of pentavalent contamination to this, a piece of the p-type Si will get changed over to n-type silicon. This sheet will currently contain both p-type district and n-type locale and an intersection between these two areas.
• The cycles that trail the development of a p-n intersection are of two sorts – dissemination and float. As we probably are aware, there is a distinction in the convergence of openings and electrons at the different sides of an intersection, the openings from the p-side diffuse to the n-side and the electrons from the n-side diffuse to the p-side. These lead to a dispersion current across the intersection.

### Biasing conditions for the p-n Junction Diode

There are two working areas in the p-n intersection diode:

1. p-type
2. n-type

There are three biasing conditions for p-n intersection diode and this depends on the voltage applied:

• Zero bias: There is no outside voltage applied to the p-n intersection diode.
• Forward bias: The positive terminal of the voltage potential is associated with the p-type while the adverse terminal is associated with the n-type.
• Invert bias: The adverse terminal of the voltage potential is associated with the p-type and the positive is associated with the n-type.

Forward Bias

• At the point when the p-type is associated with the positive terminal of the battery and the n-type to the adverse terminal then the p-n intersection is supposed to be forward-one-sided. At the point when the p-n intersection is forward one-sided, the underlying electric field at the p-n intersection and the applied electric field are in inverse ways.
• When both the electric fields add up, the resultant electric field has an extent lesser than the implicit electric field. This outcome in a less resistive and more slender exhaustion area. The exhaustion area’s obstruction becomes unimportant when the applied voltage is huge.
• In silicon, at the voltage of 0.6 V, the opposition of the exhaustion district turns out to be totally unimportant and the current streams across it unobstructed.

Reversed Bias

• At the point when the p-type is associated with the adverse terminal of the battery and the n-type is associated with the positive side then the p-n intersection is supposed to be converse one-sided.
• For this situation, the inherent electric field and the applied electric field are similar way. At the point when the two fields are added, the resultant electric field is in a similar way as the underlying electric field making a more resistive, thicker consumption district.
• The consumption locale turns out to be more resistive and thicker if the applied voltage increases.

### Zener Diode

A Zener diode is a vigorously doped semiconductor gadget that is intended to work the opposite way.

A Zener Diode, otherwise called a breakdown diode, is an intensely doped semiconductor gadget that is intended to work the converse way. At the point when the voltage across the terminals of a Zener diode is turned around and the potential arrives at the Zener Voltage (knee voltage), the intersection separates and the current streams the opposite way. This impact is known as the Zener Effect.

Zener Diode work in Reverse Bias

A Zener diode works actually like an ordinary diode when it is forward-one-sided. Notwithstanding, when associated with backwards one-sided mode, a little spillage current moves through the diode. As the opposite voltage increments to the foreordained breakdown voltage (Vz), current beginnings coursing through the diode. The current increments to the greatest, which is dictated by the series resistor, after which it balances out and stays steady over a wide scope of applied voltage.

There are two kinds of breakdowns for a Zener Diode:

• Avalanche Breakdown
• Zener Breakdown
• Avalanche Breakdown in Zener Diode:

Avalanche breakdown happens both in ordinary diode and Zener Diode at high opposite voltage. At the point when a high worth of opposite voltage is applied to the PN intersection, the free electrons acquire adequate energy and speed up at high speeds. These free electrons moving at high speed impacts different molecules and knocks off more electrons.

Because of this consistent impact, an enormous number of free electrons are produced because the electric flow in the diode quickly increments. This abrupt expansion in electric flow may forever obliterate the ordinary diode, nonetheless, a Zener diode is intended to work under torrential slide breakdown and can support the unexpected spike of flow. Torrential slide breakdown happens in Zener diodes with Zener voltage (Vz) more prominent than 6V.

• Zener Breakdown in Zener Diode:

At the point when the applied converse predisposition voltage arrives nearer to the Zener voltage, the electric field in the exhaustion locale gets sufficiently able to pull electrons from their valence band.

The valence electrons that acquire adequate energy from the solid electric field of the exhaustion area break liberated from the parent molecule. At the Zener breakdown district, a little expansion in the voltage brings about the fast increment of the electric flow.

Avalanche Breakdown vs Zener Breakdown:

• The Zener impact is predominant in voltages up to 5.6 volts and the torrential slide impact takes over that.
• They are both comparative impacts, the distinction being that the Zener impact is a quantum wonder and the Avalanche Breakdown impact is the development of electrons in the valence band like in any electric flow.
• Avalanche Breakdown impact likewise permits a bigger current through the diode than what a Zener breakdown would permit.

### Circuit Symbol of Zener Diode

There are numerous manners by which a Zener diode is bundled. Some are utilized for significant degrees of force dissemination and the others are contained with surface mount designs. The most widely recognized kind of Zener diode is contained inside a little glass epitome. It has a band around one end denoting the cathode side of the diode.

Symbol of Zener Diode

### V-I Characteristics of Zener Diode

The graph given underneath shows the V-I qualities of the Zener diode.

Pictorial representation of V-I characteristics

The V-I qualities of a Zener diode can be separated into two sections as follows:

• Forward Characteristics of Zener Diode: The primary quadrant in the diagram addresses the forward qualities of a Zener diode. From the diagram, we comprehend that it is practically indistinguishable from the forward attributes of some other p-n intersection diode.
• Reverse Characteristics of Zener Diode: At the point when an opposite voltage is applied to a Zener voltage, at first a little converse immersion current Io streams across the diode. This current is because of thermally created minority transporters. As the opposite voltage is expanded, at a specific worth of converse voltage, the converse current increments definitely and forcefully. This means that the breakdown has happened. We call this voltage breakdown voltage or Zener voltage and it is signified by Vz.

### Zener Diode Specifications:

Some normally utilized details for Zener diodes are as per the following:

• Zener/Breakdown Voltage – The Zener or the opposite breakdown voltage goes from 2.4 V to 200 V, at times it can go up to 1 kV while the greatest for the surface-mounted gadget is 47 V.
• Current Iz (max) – It is the greatest current at the evaluated Zener Voltage (Vz – 200μA to 200 A)
• Current Iz (min) – It is the base worth of current needed for the diode to break down.
• Force Rating – It signifies the most extreme force the Zener diode can disperse. It is given by the result of the voltage of the diode and the current moving through it.
• Temperature Stability – Diodes around 5 V have the best security
• Voltage Tolerance – It is ordinarily ±5%
• Zener Resistance (Rz) – It is the protection from the Zener diode shows.

### Applications of  Zener Diode

Following are the uses of Zener diode:

1) Zener diode as a voltage regulator: Zener diode is utilized as a Shunt voltage controller for managing voltage across little loads. The breakdown voltage of Zener diodes will be steady for a wide scope of current. Zener diode is associated corresponding to the heap to make it switch predisposition and when the Zener diode surpasses knee voltage, the voltage across the heap will become consistent.

2) Zener diode in over-voltage protection: At the point when the info voltage is higher than the Zener breakage voltage, the voltage across the resistor drops bringing about a short out. This can be kept away from by utilizing the Zener diode.

3) Zener diode in clipping circuits: Zener diode is utilized for adjusting AC waveform cutting circuits by restricting the pieces of it is possible that one or both the half patterns of an AC waveform.

### Sample Questions

Question 1: What is Zener diode?

A Zener Diode, otherwise called a breakdown diode, is an intensely doped semiconductor gadget that is intended to work the converse way. At the point when the voltage across the terminals of a Zener diode is turned around and the potential arrives at the Zener Voltage (knee voltage), the intersection separates and the current streams the opposite way. This impact is known as the Zener Effect.

Question 2: What is the Reverse bias condition?

At the point when the p-type is associated with the adverse terminal of the battery and the n-type is associated with the positive side then the p-n intersection is supposed to be converse one-sided. For this situation, the inherent electric field and the applied electric field are a similar way. At the point when the two fields are added, the resultant electric field is a similar way as the underlying electric field making a more resistive, thicker consumption district. The consumption locale turns out to be more resistive and thicker if the applied voltage increases.

Question 3: What is avalanche breakdown in the Zener diode?

Avalanche breakdown happens both in ordinary diode and Zener Diode at high opposite voltage. At the point when a high worth of opposite voltage is applied to the PN intersection, the free electrons acquire adequate energy and speed up at high speeds. These free electrons moving at high speed impacts different molecules and knocks off more electrons. Because of this consistent impact, an enormous number of free electrons are produced because of electric flow in the diode quickly increments. This abrupt expansion in electric flow may forever obliterate the ordinary diode, nonetheless, a Zener diode is intended to work under torrential slide breakdown and can support the unexpected spike of flow. Torrential slide breakdown happens in Zener diodes with Zener voltage (Vz) more prominent than 6V.

Question 4: What is the distinction between a Zener diode and an ordinary diode?

The principle contrast between a Zener diode and an ordinary diode lies in the entry of current. An ordinary diode permits current to stream just one way while Zener diode permits current to stream in the two ways.

Question 5: What are the applications of Zener diode?

Following are the applications of Zener diode:

1) Zener diode as a voltage regulator

2) Zener diode in over-voltage protection

3) Zener diode in clipping circuits

Question 6: How Zener diode works in reverse bias conditions?