In the forward bias condition, the zener diode behaves like an ideal diode within specified current and power limits, but it differs in reverse bias condition where the zener diode has very steep avalanche characteristic at the breakdown voltage in reverse bias condition. In zener diode, electric current flows from both anode to cathode and cathode to anode. A zener diode is a special kind of diode which allows current to flow in the forward direction in the same manner as an ideal diode, but will also permit it to flow in the reverse direction. Aug 09, 2019 zener diode allows current just like a simple pn junction diode when it is forward bias but it also allows current when its reverse bias if the applied reverse voltage is greater than the zener voltage zeners have particular zener voltage which indicates that this diode will regulate voltage up to this limit. If you had that query in your mind, then reading further would give you a thorough knowledge on the discovery of zener diode and its properties. The zener diode is a particular type of diode that solves this problem. Recipe for solving diode circuits state of diode is unknown before solving the circuit 1. V z0 is the voltage at which the straightline approximation of the iv characteristic intersects the horizontal axis. The very steep portion in the reverse biased iv characteristic curve is. In order to understand zener diode operation let us first recall the vi characteristic of a.
Basic electronics notes on vi characteristics of zener diode in pdf. The forward characteristics of a zener organic chemistry smith. The right half side of the characteristics curve is the part in which the zener diode receives forward voltage, which is positive voltage across its anode to cathode terminals. A zener diode is a special kind of diode which allows current to flow in the forward direction in the same manner as an ideal diode, but will also permit it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage, zener knee voltage or zener voltage. For zener diodes, silicon is preferred to ge because of its high temperature and. On increasing the reverse voltage, current increases. For the zener diode we are using a model with a breakdown voltage vz and an effective. Zener voltage z 1 10 100 1,000 1 10 100 v, zener voltage v fig. Use the diode equation for that state to solve the circuit equations and find i d and v d 3. Thus, zener diodes protect it from damage by providing voltage regulation. This was a bad thing before the whole avalanche breakdown, large current. Basic electronics notes on vi characteristics of zener diode.
The circuit symbol of zener diode is as shown in the figure. Zener diode definition, vi characteristics, and breakdown. Jan 02, 2019 the zener diode is a particular type of diode that solves this problem. This type of diode is called a zener diode, and its symbol looks like figure above b. Typically, a silicon diode will have a vf around 0. The forward characteristics of zener diode are similar to that of normal pn. We operate a zener diode in reverse biased conditions, and this diode does not get damaged even when the voltage across this exceeds the reverse breakdown voltage. A heavily doped semiconductor diode which is designed to operate in reverse direction is known as the zener diode. Each diode was investigated by plotting the iv curve using a precision sourcemeasurement unit b2902a and a laptop with the corresponding quick iv measurement software installed. Electronics 1 diode characteristics 1 purpose 2 objectives.
But zener breakdown voltage occurs when the reverse bias voltage is greater than a predetermined voltage. Electrical characteristics tamb 25 c, unless otherwise specified part number zener voltage range 1 test current reverse leakage dynamic resistance f 1 khz surge current 3 regulator 2. The vi characteristics of a zener diode is shown in the below figure. Iv characteristics uthe barrier increase reduces the majority carrier diffusion to a negligible level uthe pside electrons and nside holes can wander into the depletion region and be swept to the other side a reverse inap ureverse bias situation aan increase of the potential hill ubeing associated with. The iv characteristic curve of the diode is shown on figure 1b. Semiconductor is basically a pn junction where the ptype silicon contacts with the ntype. It is the reverse biased havily doped silicon or germanium pn junction diode which is operated in the breakdown region where current is limited by both external resistance and power dissipation of the diode. In normal diodes, the breakdown voltage is very high and the diode gets damaged totally if a voltage above the breakdown diode is applied, but in zener diodes, the breakdown voltage is not as high and does not lead to permanent damage of the zener diode if the voltage is applied as the reverse voltage applied to the zener diode increases towards the. The vi characteristic of zener diode indicates that characteristic of zener diode in forward bias is same as pn junction diode. Silicon is preferred to diode because of its higher temperature and current capability.
Zener diodes are heavily doped than ordinary diodes. It can be designed to have a breakdown voltage over a wide range from 0. Diode, resistor, variable dc power supply, milliammeter, voltmeter, rheostat and wire. Physics lab manual by comprehensive adobe illustrations bibliography. And while that sounds a bit esoteric, theyre actually among the handiest components ever to cross an engineers bench. Zener diode examples and circuit analysis book pdf by alvin. Z ener diode as the name suggests is a two terminal device with two terminals being anode p and cathode n. Zener diode this voltage regulator is a pn junction diode that has a precisely tailored impurity distribution to provide a welldefined breakdown voltage.
The zener diode working principles and its various. The zener diode goes through a number of different regions or stages, of which are explained below. Zener diode is used for voltage regulation purpose. When we apply a voltage more than the zener breakdown voltage can range from 1. Reverse biasing will generally not cause current conduction until higher values of reverse voltage are reached. You will make iv curves for each and will see how a diode can be used as a voltage recti. The voltage at which zener diode conducts in reverse bias is called as zener voltage vz.
In other words, the diode which is specially designed for optimising the breakdown region is known as the zener diode. Zener diodes are normal pn junction diodes operating in a reverse biased condition. Pdf zener diode today we will discuss about a special diode known as zener diode. Before going into the invention story, let us have a brief note on what a zener diode is. Zener diode zener regulator other zener diode regulators zener diode parameters practical applications of diode circuits dr. Let us learn about this exciting and unique kind of diode. Excerpts of the data sheets for the zener diodes you used in the laboratory, including a discussion. Diode characteristics 2012 summary this experiment was set up to investigate the different properties and characteristics of several different types of diode. Zener diode is nothing but a single diode connected in a reverse bias mode and zener diode can be connected in reverse bias positive in a circuit as shown as picture. Zener diode characteristics, working and applications. Zener diode lab viva questions and answers pdf free download. The circuit diagram to plot the vi characteristics of a zener diode is shown.
Write down all circuit equations and simplify as much as possible 2. The symbolic representation of zener diode is shown in the figure below. The zener regulator is composed of resistor r1 and zener diode. The other differences between the pnjunction and zener diode are shown in the comparison chart. Unfortunately, when normal rectifying diodes break down, they usually do so destructively.
Zener diodes are normally used only in the reverse bias direction. The symbol of zener diode is shown in the figure below. The vi characteristics of a zener diode is as shown in the figure below. Basic electronics notes on vi characteristics of zener. Explain how normal diodes might be used as crude substitutes for a zener diode in the following circuit. Jun 12, 2016 voltage vs current characteristics of 5. Ele230 electronics i11mar2017 1 30 diode applicationsclippers clippers clipper diode circuits have the ability to clip o a portion of the input signal without. The zener diodes breakdown characteristics are determined by the doping process. Zener diode characteristics zener regulator prelab. Zener diodes when we first talked about practical diodes, it was mentioned that a parameter associated with the diode in the reverse bias region was the breakdown voltage, v br, also known as the peakinverse voltage piv. The vi characteristics or voltagecurrent characteristics of the pn junction diode is shown in the below figure. Diode circuits and applications technology innovation and.
Zener diodes the simplest of all voltage regulators is the zener diode voltage regulator. To draw the characteristics curve of a zener diode and determine its iz zener. A zener diode is constructed for operation in the reverse breakdown re gion. The symbol of zener diode is similar to the normal pn junction diode, but with bend edges on the vertical bar. The breakdown voltage of a zener diode can be set by controlling the doping level. Zener diode is same as the normal pn diode but specially designed to operate in reverse bias. When zener diodes are biased in their forward direction, with the anode voltage higher than the cathode, they behave in the same way as a normal silicon diode. Conduct the experiment for obtaining the forward bias vi characteristics of the given diode. In normal diodes, the breakdown voltage is very high and the diode gets damaged totally if a voltage above the breakdown diode is applied, but in zener diodes, the breakdown voltage is not as high and does not lead to permanent damage of the zener diode if the voltage is applied. This file covers the topic of zener diode to study its vi. In reverse biased condition, a small reverse current flows due to minority charge carriers. Zener diode is a simplest type of voltage regulator. This is to compensate for the damage that occurs in the case of a pn junction diode when the reverse bias exceeds the breakdown voltage and thereby. Zener diode working with circuit diagram and applications.
However, when reverse biased voltage is applied to the zener diode, it works in different manner. Due to its doping characteristics, the zener diode is made to use at high breakdown voltage. The value of the resistance is the inverse of the slope of the iv characteristics of the zener diode d all of the mentioned. In this lesson we define the zener diode and describe its characteristics. The type of diode also has some importance in defining the forward voltage drop. Zener diode examples and circuit analysis book pdf by. These documents describe testing for static relays for. It means that the anode must be connected to the negative side of the voltage source and the cathode must be connected to the positive side. Schematic va characteristics of avalanche or zener diode. Zener diode characteristics in the forward region, the zener diode acts like a regular silicon diode, with a 0. Zener diodes are simple and useful devices for building voltage regulator circuits, but are times when you may have to improvise in the absence of the proper zener diode.
Zener doide is a special diode with increased amounts of doping. Zener diode as voltage regulator and its vi characteristics. Electrical engineering department power diode characteristics electrical engineering division page 2 of 8 eg 405. A zener diode is a special diode that is optimized for operation in the breakdown region. Forward biasing will cause a large if with a rather small value of vf. Reverse biasing will generally not cause current conduction until. Pdf zener diode pdf zener diode pdf zener diode download. Zener diode operation and applications ece tutorials. The iv characteristics of an led diode are similar to that of a regular diode except that the forward voltage may. You shall also be informed of the great scientists who worked on this device.
In reverse bias, a negligible constant current flow through the zener diode but the current becomes abruptly large at certain voltage. Electronics 1 diode characteristics adam fifth rowan university february 12, 2019 1 purpose the purpose of this lab is to measure the properties of a diode, zener diode, and led. Working of the zener diode is similar to a pn junction diode in forward biased condition, but the uniqueness lies in the fact that it can also conduct when it is connected in reverse bias above its threshold breakdown voltage. The zener regulator is composed of resistor r1 and zener diode cr1 the resistor characteristics are shown in table iv. Keep the multisim file handy to refer it to in the lab. Zener diodes are designed for specific reverse breakdown voltage called zener breakdown voltage vz. Diode circuits operating in the reverse breakdown region. We will focus our analysis in the reverse bias region of the iv curve. In some cases, excess current flows through a circuit and damage the multimeter. Zener diode experiment viva questions with answers characteristics mcqs interview questions. Zener diodes are a special type of semiconductor diode devices that allow current to flow in one direction only that also allow current to flow in the opposite direction, but only when exposed to enough voltage. In simple words, it regulates maintain the voltage across its terminal when it is in reverse biased it is consisting of two terminals one is an anode and another is cathode kathode. A main difference between zener diodes and regular silicon diodes is the way they are used in the circuits.
However, it is possible to build a special type of diode that can handle breakdown without failing completely. A pin diode is a semiconductor device that operates as a variable resistor at rf and microwave frequencies. Zener diodes can also withstand higher reverse current flow than comparable pn diodes, and are available with various power ratings, typically from 500mw to 50w. Experimently find out whether the given diode is made of germanium or silicon. A zener diode is constructed for operation in the reverse breakdown region. A specific diodes vf depends on what semiconductor material its made out of. Zener diode operation let us first recall the vi characteristic of a. The characteristics of a regular junction diode will show that it is designed primarily for operation in the forward direction. Permission is granted to copy, distribute andor modify this document under the terms of the gnu free documentation license, version 1. Ahmed reverse recovery characteristics when a diode is in forward conduction mode, a sudden reversal of the polarity of the applied voltage would not stop the diode current at once.
The reverse breakdown of a pn junction may occur either due to zener effect or avalanche effect. A specific diode s vf depends on what semiconductor material its made out of. Zener diode is a reversebiased heavilydoped pn junction diode which operates in the breakdown region. This article will help to explain the characteristics which make up zener diodes, specifically how the voltage across a zener diode varies with the current flowing through it. The forward characteristic of the zener diode is similar to a normal diode which is clearly seen in the figure above. When forward biased voltage is applied to the zener diode, it works like a normal diode. Also, we describe how the zener diode is used as a voltage regulator, a clipping circuit and as a voltage reference. Vz is the reverse breakdown voltage and vg is the forward voltage drop across the diode. Analysis and measurement of a zener diode voltagereference.
In this region the voltage across zener diode remains constant but current changes depending on the supply voltage. The zener diode is a special type of diode that is designed to work in the reverse breakdown region. A diode, in electronics, is a two terminal electronic component with an asymmetric transfer characteristics, with low resistance to current flow in one direction and high resistance to current flow in the other direction. The iv characteristic curve and diode symbols for the regular and zener diodes are given to the right figure 3. The signal diode is a silicon doped semiconductor diode or a germanium doped diode but depending up on the do ping material the characteristics of the diode varies. Forward biasing will cause a large i f with a rather small value of v f. The complete vi characteristics of zener diode is as shown in figure. In forward bias, the characteristics of zener diode are same as standard pn junction diode. Basic zener regulator analysis procedure step 1 determine the state of the zener diode by removing it from the network and calculating the voltage across the resulting open.
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