The circuit symbol for a zener diodes characteristics in fig. 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. To draw the characteristic curve of a zener diode and to. A zener diode is a pn junction semiconductor device that is designed to operate in the. This was a bad thing before the whole avalanche breakdown, large current.
Zener diode is a reverse biased heavily doped semiconductor silicon or germanium pn junction diode, which is operated exclusively in the breakdown region. Zener diodes are widely used as voltage references and as shunt regulators to regulate the voltage across small circuits. The figure below shows the characteristic curve of a zener diode. When connected in parallel with a variable voltage source so that it is reverse biased, a zener diode conducts when the voltage reaches the diode s reverse breakdown voltage. It provides the constant voltage from the fluctuating voltage source to the load. A zener diode is a special diode that is optimized for operation in the breakdown region. When high reverse voltage is applied to the pn junction diode, the free. The breakdown potential, also called the zener potential i. A zener diode is a type of diode that allows current to flow in the conventional manner from its anode to its cathode i. Diode a diode is a specialized electronic component with two electrode called the anode and the cathode. Zener diode as voltage regulator and its vi characteristics. In the forward biased mode the zener diode operates as a pn diode. Vi characteristics of zener diode vi characteristics of pn.
When the voltage across the terminals is reversed and the potential reaches the zener voltage or knee, the junction will break down and current will flow in the reverse direction a desired characteristic. Full practical zener diode with readings download pdf. Because of its unusual properties it fills a longstanding need in electronic circuitry. Electronics tutorial about the pn junction diode and the vi characteristics of pn. Archived from the original pdf on february 23, if tighter tolerance is required, consult. It is acting as normal diode while forward biasing. Zener diode characteristics in the forward region, the zener diode acts like a regular silicon diode, with a 0. Sep 08, 2018 this video lecture explains the vi characteristics of the zener diode. In this region the voltage across zener diode remains constant but current changes depending on the supply voltage. The following are the main application of the zener diode. 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. However, the main differences between them is that the latter is a controlled device when it is turned on.
In the vi characteristics above vz is the zener voltage. User may specify either, both, or neither of the at least and no more than values. Zener diode symbol zener diode circuit zener diode vi characteristics zener diode working zener diode applications faqs. The symbol of zener diode is similar to the normal pn junction diode, but with bend edges on the vertical bar. A free powerpoint ppt presentation displayed as a flash slide show on id. Its characteristics are otherwise very similar to common diodes. However, it is possible to build a special type of diode that can handle breakdown without failing completely. The relationship is obtained by applying kvl and it is vs vg r im. Zener diode working, characteristics and application as. The zener regulator is composed of resistor r1 and zener diode cr1 the resistor characteristics. Ammeter circuit diagram theory zener diode is a pn junction diode specially designed to operate.
Hbd854 zener theory and design considerations handbook. The iv characteristics are the variation of current for the applied voltage. Diode circuits operating in the reverse breakdown region. Primary characteristics parameter value unit vz range nom. Also, we describe how the zener diode is used as a voltage regulator, a clipping circuit and as a voltage reference. A semiconductor diode is the most common type diode, which is a piece of semiconductor material with a pn junction connected to two terminals.
Zener diode definition 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 breakdown voltage known as zener knee. The contact surface between the layers of ptype and ntype semiconductor pieces plated together so as to form a pn junction is called the pn junction. Ppt zener diode applications powerpoint presentation free. 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. Zener diodes if we connect a diode and resistor in series with a dc voltage source so that the diode is forwardbiased, the voltage drop across the diode will remain fairly constant over a wide range of power supply voltages as in figure below a. For zener diodes, silicon is preferred to ge because of its high. The forward characteristic of the zener diode is similar to a normal diode which is clearly seen in the figure above. Basic electronics notes on vi characteristics of zener. A diode can be defined as the fundamental electronic component that allows the flow of electricity in one direction only. 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 behaviour of a diode in a circuit is given by its iv characteristics. This video lecture explains the vi characteristics of the zener diode.
A zener diode is heavily doped to reduce the reverse breakdown voltage. The vi characteristics or voltagecurrent characteristics of the pn junction diode is shown in the below figure. Basic electronics notes on vi characteristics of zener diode. 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. As voltage stabilizer the zener diode is used for regulating the voltage. To draw the characteristic curve of a zener diode and to determine its reverse breakdown voltage aim to draw the characteristic curve of a zener diode and to determine its reverse breakdown voltage. The zener diode is a particular type of diode that solves this problem. Zener diode is a special kind of diode which permits the flow of current in the forward direction as well as in reverse direction when the voltage is above a certain voltage known as breakdown or zener voltage. V i characteristics are used for explaining the relationship between voltage and current characteristics of any given electrical component. Zener diodes cannot be tested individually with a multimeter. The nonlinear, and polarity characteristics of the diode make for a very interesting and useful device albeit at the expense of added complexity of circuit design and analysis. Zener diodes characteristics circuit symbol equivalent. In the case of normal diodes the diode damages at the break down voltage. Vi characteristics of pn junction diode in 3biasing modes.
Tunnel diode basics, operation, vi characteristics. A specific diode s vf depends on what semiconductor material its made out of. Jan 02, 2019 the above diagram shows the v i characteristics of a zener diode. Vi shay disclaims i any and al l liability arising out of the application or use of any product, ii any and all liability, including without limitation special.
When the diode is connected in forward bias, this diode acts as a normal diode but when the reverse bias voltage is greater than zener voltage, a sharp breakdown takes place. Zener diode experiment viva questions with answers characteristics mcqs interview questions. Aim to plot the reverse characteristics of zener diode and to find the breakdown voltage components and equipments needed 1. Most diodes are made with semiconductor materials such as silicon, germa. This type of diode is called a zener diode, and its symbol looks like figure above b. The heart of the zener voltagereference is shown in the. This manual was prepared to acquaint the engineer, the equipment designer and. A zener diode is constructed for operation in the reverse breakdown re gion. To plot the vi characteristics of a zener diode in reverse wise.
The zener diode is a special type of diode that is designed to work in the reverse breakdown region. When making zener impedance measurements at the i zk test point, it may be necessary to insert a 60 hz band pass filter between the diode and voltmeter to avoid errors resulting from low level noise signals. In this lesson we define the zener diode and describe its characteristics. The circuit symbol of zener diode is as shown in the figure. It has a particular voltage known as break down voltage, at which the diode break downs while reverse biased. A zener diode is a type of diode that allows current to flow in the conventional manner from its. Therefore, this is all about pn junction diode in zero bias, forward bias and reverse bias conditions and vi characteristics of pn junction diode. Zener diode definition, vi characteristics, and breakdown in zener.
The circuit shown on figure 1a will be used to explore the characteristics of operation in the breakdown region. Jan 29, 2019 although zener and avalanche are two different types of breakdown, the name zener diodes characteristics is commonly applied to all breakdown diodes. Zener diode is a pn junction diode specially designed for operation in the breakdown region in reverse bias condition. Zener diodes design support tools available features. Products returned as matches will meet all specified criteria. The symbol of a zener diode is shown in fig for normal operation of a zener diode, in breakdown region, the current through the diode should be limited by an external circuit. A voltage stabilizer is a combination of elements that are designed to ensure the output voltage of a supply fairly remains constant. After the point v v, the tunnel diode behaves as a normal diode.
When a zener diode operates in the breakdown region, it does not burn rapidly. The figure represents the curve for both silicon and germanium diodes. The complete v i characteristics of zener diode is as shown in figure. Unfortunately, when normal rectifying diodes break down, they usually do so destructively. Jan, 20 the characteristics of a regular junction diode will show that it is designed primarily for operation in the forward direction.
It provides, among other useful functions, a constant voltage reference. Schesser 182 zener diodes operated in the breakdown region. Zener diode lab viva questions and answers pdf free download. Zener diode theory introduction the zener diode is a semiconductor device unique in its mode of operation and completely unreplaceable by any other electronic device. The vi characteristics of a zener diode is shown in the below figure.
The type of diode also has some importance in defining the forward voltage drop. Zener diodes are designed to operate in the reverse breakdown region and circuits containing them provide voltage regulation or voltage referencing. Vi characteristics of zener diode vi characteristics of. The zener diode is connected in parallel across the load and maintain the constant voltage v z and hence stabilises the voltage. The voltage at which the zener diode breaks down is called the zener voltage. By using an led and a zener diode we can create a circuit which gives turns on the led when a voltage exceeds a certain value. 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.
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. It is because multimeters usually do not have enough input voltage to put the zener into breakdown region. The diode is two terminal non linear device whose iv characteristic besides exhibiting nonlinear behavior is also polarity dependent. Zener diode is a pn junction diode specially designed to operate in the reverse biased mode. Zener diode applications chapter 3 overview zener diodes zener characteristics zener diodes diode types rectifier zener lower vz due to more heavily. A diode allow electric current to pass in forward direction and block current in reverse direction. The contact surface between the layers of ptype and ntype semiconductor pieces plated together so as. However, when reverse biased voltage is applied to the zener diode, it works in differen. Ppt zener diode applications powerpoint presentation. The free carriers created through this collision contribute to the reverse current. Typically, a silicon diode will have a vf around 0. However, when reverse biased voltage is applied to the zener diode, it works in different manner. The v i characteristic of scr, mosfet, led, pn junction diode, and zener diode is explained here. 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.
Permission is granted to copy, distribute andor modify this document under the terms of the gnu free documentation license, version 1. Zener diode definition, vi characteristics, and breakdown. Experimently find out whether the given diode is made of germanium or silicon. Basic electronics notes on vi characteristics of zener diode in pdf. A copy of the license is included in the section entitled gnu free documentation license. Electrical engineering department power diode characteristics electrical engineering division page 2 of 8 eg 405. The figure above shows the combine characteristics of zener breakdown zener diode and avalanche breakdown it is noted that both breakdowns occur when a diode is in reverse bias condition. In reverse bias, a negligible constant current flow through the zener diode but the current becomes abruptly large at certain voltage. Analysis and measurement of a zener diode voltagereference. But zener breakdown voltage occurs when the reverse bias voltage is greater than a predetermined voltage. April 7, 20 introduction a zener diode is a pn junction that has been specially made to have a reverse voltage breakdown at a specific voltage. Zener diodes the simplest of all voltage regulators is the zener diode voltage regulator.
Forward biasing will cause a large i f with a rather small value of v f. Zener diode this voltage regulator is a pn junction diode that has a precisely tailored impurity distribution to provide a welldefined breakdown voltage. Zener voltage v z is the reverse voltage at which breakdown occurs in a zener diode search logic. Pn junction diode vi characteristics in reverse bias. By applying a negative voltage reverse bias results in the free charges. The other differences between the pnjunction and zener diode are shown in the comparison chart. As the forward voltage starts to increase, the diode current raises rapidly due to tunnel effect. The vi characteristic of zener diode indicates that characteristic of zener diode in forward bias is same as pn junction diode. It can be designed to have a breakdown voltage over a wide range from 0. When forward biased voltage is applied to the zener diode, it works like a normal diode. Conduct the experiment for obtaining the forward bias vi characteristics of the given diode. We hope that you have got a better understanding of this concept.
Here you will learn, how the zener diode is used in reverse biasing. In our previous articles, we explain in detail about diodes, pn junction diode, semiconductors etc. Iv characteristics of zener diode make it suitable for application such as a voltage regulator. Zener diodes are heavily doped than ordinary diodes. 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. The breakdown voltage of a zener diode can be set by controlling the doping level.
To get breakdown voltage sharp and distinct doping is controlled and the surface imperfections are avoided. Some of the more common specialpurpose diodes are i zener diode ii lightemitting diode led iii photo diode iv tunnel diode v varactor diode and vi shockley diode. In the reverse biased mode zener diode has large breakdown voltage and though the current increases the voltage remains constant. A zener diode is a 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. However, the reason for this is some external circuit is required in order to protect the device from the excess current. After the point v p, the tunnel effect is reduced and current flow starts to decrease even though increase in voltage ie negative resistance region. In this article, we are going to explain zener diode and its applications in detail. The value of the resistance is the inverse of the slope of the iv characteristics of the zener diode d all of the mentioned. Apparatus a zener diode with small reverse breakdown voltage of about 6 volts, i. Zener diode working with circuit diagram and applications. An ordinary diode operated in this region will usually be destroyed due to excessive current. The horizontal line in the below figure represents the amount of voltage applied across the pn junction diode whereas the vertical line represents the amount of current flows in the pn junction diode. Jan 02, 2019 the zener diode is a particular type of diode that solves this problem. In zener diode, electric current flows from both anode to cathode and cathode to anode.
1592 1195 166 1467 700 858 1162 209 807 401 456 40 1418 493 1105 469 402 874 242 113 364 1204 227 1202 92 1217 152 705 198 988 828 230 193 1378 663 47