The inputoutput characteristics with idealand constantvoltagemodels yields two different break points. Zener diode definition, vi characteristics, and breakdown in zener. 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. Zener diode symbol zener diode circuit zener diode vi characteristics zener diode working zener diode applications faqs. The vi characteristics or voltagecurrent characteristics of the pn junction diode is shown in the below figure. V i n v z is a necessary condition for the zener diode to work as a voltage regulator. The iv characteristics curve of a zener diode, shown below, is the curve which shows the current. When the doping is heavy, even the reverse voltage is low, the electric field at barrier will be so strong thus the electrons in the covalent bonds can break. The characteristics of a regular junction diode will show that it is designed primarily for operation in the forward direction.
A zener diode of break down voltage v z is reverse connected to an input voltage source v i across a load resistance r l and a series resistor r s. The symbol of zener diode is similar to the normal pn junction diode, but with bend edges on the vertical bar. Dec 02, 2016 to draw the characteristic curve of a zener diode and to determine its reverse breakdown voltage. A semiconductor diode is the most common type diode, which is a piece of semiconductor material with a pn junction connected to two terminals. Ab0l is a compact, ready to use diode characteristics experiment board. A zener diode is heavily doped to reduce the reverse breakdown voltage. Zener diode is a reverse biased heavily doped semiconductor silicon or germanium pn junction diode, which is operated exclusively in the breakdown region. 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. The i v characteristics curve of a zener diode, shown below, is the curve which shows the current. A zener diode is constructed for operation in the reverse breakdown re gion.
Building a voltage regulator with an ideal zener diode, construction of a voltage. To draw the characteristic curve of a zener diode and to determine its reverse breakdown voltage. A zener diode with small reverse breakdown voltage of about 6 volts, i. Vi characteristics of zener diode vi characteristics of pn.
Forward biasing will cause a large if with a rather small value of vf. However, unlike a resistor, a diode does not behave linearly with respect to the applied voltage as the diode has an exponential currentvoltage iv relationship and therefore we can not. We use zener diodes for voltage regulation and voltage stabilisation. 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. A zener diode is constructed for operation in the reverse breakdown region. The relationship is obtained by applying kvl and it is vs vg r im.
But for simplicity, both types are called zener diodes. In on state, the voltage across zener diode remains constant until the voltage across it deops less than vz. Basic electronics notes on vi characteristics of zener diode in pdf. Diodes which are designed with adequate power dissipation capabilities to operate in the break down region are called as break down or zener diodes. The pn junction diode is a twoterminal device, which is formed when one side of the pn junction diode is made with ptype and doped with the ntype material. V z v l is a constant dependent on the zener diode. When a forward voltage is applied, current flows through it. Forward biasing will cause a large i f with a rather small value of v f. If you took your data from both modes of operation and plotted it on a linear scale it would look similar to figure 2.
To plot the vi characteristics of a zener diode in reverse wise. They provide a lowcost and no frill method for voltage regulation. When reverse biased, a small reverse current known as leakage current flows. Pdf explain a little about the zener diode sina taherinasab. Zener diode, vi characteristics, working, and applications. The page explains forward biased condition and reverse biased condition of an ideal diode. A zener diode is a type of diode that allows current to flow in the conventional manner from its anode to its cathode i. When the zener diode is connected, in forward bias, diode acts as a normal diode. V z0 is the voltage at which the straightline approximation of the i v characteristic intersects the horizontal axis. The function of a regulator is to provide a constant output voltage to a load connected in parallel with it in spite of the ripples in the supply voltage or the variation in the load current. Circuit diagram for usage of zenerdiode as a voltage regulator is shown in the attached figure. Basic electronics notes on vi characteristics of zener. It is acting as normal diode while forward biasing. Vi characteristics of pn junction diode in 3biasing modes.
This leakage current increases with increase in magnitude of reverse voltage until avalanche voltage is reached breakdown voltage. The heart of the zener voltagereference is shown in the. Tunnel diode basics, operation, vi characteristics. This video lecture explains the vi characteristics of the zener diode. 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. Voltampere vi characteristics of a pn junction or semiconductor diode is the curve between voltage across the junction and the current through the circuit. 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.
Zener diode as voltage regulator and its vi characteristics. If the positive terminal of the battery is connected to the ptype semiconductor and the negative terminal of the battery is connected to the ntype semiconductor, the diode is said to be in forward bias. Figure 1 shows the vi characteristics of a typical zener diode. The basic purpose of a power supply is to provide one or more fixed voltages to the working circuit, with sufficient current handling capacity to maintain the operating conditions of the circuit. Jan 21, 2019 voltampere v i characteristics of a pn junction or semiconductor diode is the curve between voltage across the junction and the current through the circuit. Draw the reverse characteristics of zener diode and determine its break down voltage. 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 circuit connection for determining the vi characteristics of a pn junction is shown in the figure below. The critical parameter of this type of diodes is the zener breakdown voltage. It has a particular voltage known as break down voltage, at which the diode break downs while reverse biased. A diode allow electric current to pass in forward direction and block current in reverse direction. The zener voltage is an essential parameter for choosing a zener diode for particular voltage regulation application. From the iv characteristics curve above, we can see that the zener diode has a region in its reverse bias characteristics of almost a constant negative voltage regardless of the value of the current flowing through the diode. The tunnel diode was first introduced by leo esaki in 1958.
The v i characteristic curve for the zener diode is shown in fig. The behaviour of a diode in a circuit is given by its iv characteristics. The circuit diagram to plot the vi characteristics of a zener diode is shown. There are several drawbacks, however, that will be discussed shortly. This post includes explanation of operation of zener diode and v i characteristics of zener diode. Applying an inappropriate diodes model can be misleading. Figure 1 shows the v i characteristics of a typical zener diode. This property of zener diode makes its use as a voltage regulator. Sep 12, 2015 a characteristic zener diode for general purpose electronic circuits has the power rating of 500mw, bzx55 zener diode series or the larger 1. In reverse bias, a negligible constant current flow through the zener diode but the current becomes abruptly large at certain voltage. In the vi characteristics above vz is the zener voltage. 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. A pn junction diode is one of the simplest semiconductor devices around, and which has the characteristic of passing current in only one direction only. Analysis and measurement of a zener diode voltagereference.
Hbd854 zener theory and design considerations handbook. A tunnel diode is a special type of pn junction diode that shows the negative resistance between two values of forward voltage ie, between peak point voltage and valley point voltage. The zener breakdown voltage is the minimum reverse biased voltage below which the diode. The active portion of a zener diode is a semiconductor pn. However, unlike a resistor, a diode does not behave linearly with respect to the applied voltage as the diode has an exponential currentvoltage i v relationship and therefore we can not. The zener diode mainly operates in reverse biased condition. 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. An ideal diode means a perfect diode which has all properties in their perfect sense without any flaws. Zener diode vi characteristics 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. If a p and n region are heavily doped then the breakdown voltage can be reduced. 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. Usually, a diode operates either in forward or reverse biased condition. The behaviour of a diode in a circuit is given by its i v characteristics. A zener diode is a pn junction semiconductor device that is designed to operate in the reverse breakdown region.
But due to higher doping concentration, higher current flows through the zener diode. The reverse breakdown of a pn junction may occur either due to zener effect or avalanche effect. An ordinary diode operated in this region will usually be destroyed due to excessive current. The diode will be easier to understand if we compare the diode to another two terminal device we know and love the resistor. Zener diode, voltmeter 02volt, voltmeter 030 volt, miliammeter, micro ammeter, variable source 02 volt and 030 volt. When the diode is forward biased the current though the diode is. Here you will learn, how the zener diode is used in reverse biasing. This post includes explanation of operation of zener diode and vi characteristics of zener diode. The v i characteristic of zener diode indicates that characteristic of zener diode in forward bias is same as pn junction diode. Download basic electronics notes on vi characteristics of zener diode including application of zener diode voltage regulator with brief explanation in pdf. The forward biasing and reverse biasing of the zener. Zener diode working with circuit diagram and applications.
The vi characteristic of zener diode indicates that characteristic of zener diode in forward bias is same as pn junction diode. You will make iv curves for each and will see how a diode can be used as a voltage recti. But zener breakdown voltage occurs when the reverse bias voltage is greater than a predetermined voltage. Every zener diode has particular zener voltage knee voltages in that they can regulate voltage. Plot the vi characteristics and calculate the resistance levels 5. And also the knee voltage because at this point the current is the current is very rapid. The zener diode is used in its reverse bias or reverse breakdown mode, i. The diagram given below shows the v i characteristics of the zener diode.
Vi characteristics of zener diode zener diode is a reversebiased heavilydoped pn junction diode which operates in the breakdown region. The vi characteristics of a zener diode is shown in the below figure. Iv characteristics uwhenever an electron on the pside moves to the nside, it is replaced by an electron generated through one of the rg centers ohmic ohmic minority minority excess majority carriers alocal excess majority carriers alocal e e excess carriers move to the contact with a relaxation time. The circuit symbol of zener diode is as shown in the figure. Zener diode characteristics and zener as voltage regulator. 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. To draw the vi characteristic of zener diode and to determine zener breakdown voltage. Vi characteristics of zener diode vi characteristics of. This was a bad thing before the whole avalanche breakdown, large current. The voltage across the zener will remain steady at its break down voltage v z for all the values of zener current i z as long as the current remains in the break down region. The zener regulator is composed of resistor r1 and zener diode cr1 the resistor characteristics are shown in table iv. Mar 25, 2018 when a zener diode is operated in the breakdown region care must be taken to see that the power dissipation across the junction is within the power rating of the diode otherwise heavy current flowing through the diode may destroy it. The forward characteristic of a zener diode is similar to that of a p n junction diode. Reverse biasing will generally not cause current conduction until higher values of reverse voltage are reached.
Diode is reverse biased when cathode is made positive with respect to anode. Normally it is called the vi characteristics of a general p n junction diode. Zener diode has the property of behaving like a dc battery in on state i. D 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. It can be seen from the figure, that, as the reverse voltage applied to the pn junction is increased, at a particular voltage, the current increases enormously from its normal cut off value. Many early inventions were made till 1905, yet a more focused work on semiconductor devices were started only at the time of the second world war. Ideal diode and characteristics of ideal diode electrical4u. Basic electronics notes on vi characteristics of zener diode. Zener diode is a pn junction diode specially designed to operate in the reverse biased mode. Zener effect dominates at reverse voltages less than 5 volt whereas avalanche effect dominates above 5 v.
A characteristic zener diode for general purpose electronic circuits has the power rating of 500mw, bzx55 zener diode series or the larger 1. Aug 09, 2019 every zener diode has particular zener voltage knee voltages in that they can regulate voltage. The iv characteristic curve and diode symbols for the regular and zener diodes are given to the right figure 3. The characteristics which are expected to be exhibited by the ideal diode can be analyzed separately for these two modes of operation. The pnjunction is the root for semiconductor diodes. To draw the characteristic curve of a zener diode and to. Sep 08, 2018 this video lecture explains the vi characteristics of the zener diode. Characteristics of a zener diode the above diagram shows the vi characteristics of. Clarence melvin zener inventor of zener diode only when the need for semi conductor materials exceeded, the urge to develop a device like zener diode spread deeper and wider. In the case of normal diodes the diode damages at the break down voltage. Diode iv characteristics the iv graph for a nonideal diode is shown in figure 2, along with an ideal approximation to accommodate the nonzero threshold voltage. The breakdown voltage of a zener diode can be set by controlling the doping level. Exploiting this characteristic of zener diodes allows for simple, inexpensive voltage regulators. A graph of current through vs the voltage across the device is called the characteristic of zener diode.
Its characteristics are completely different from the pn junction diode. Jan 02, 2019 the page describes the experiments for determining zener voltage. The circuit connection for determining the v i characteristics of a pn junction is shown in the figure below. Normally the voltage is taken along the xaxis and current along yaxis. Zener doide is a special diode with increased amounts of doping. A diode can be defined as the fundamental electronic component that allows the flow of electricity in one direction only. It is the most essential and the basic building block of the electronic device. Zener diode definition, vi characteristics, and breakdown. The ideal diode equation is a good approximation of the diode current over selected. The 500mw, bzx55 series zener diodes are generally available in the range varying from 2. It can be used as stand alone unit with external dc power supply or can be used with. Vi characteristics of pn junction diode electronics post. For zener diodes, silicon is preferred to ge because of its high temperature and current capability. In forward bias zener works as an ordinary diode but when it is operated in reverse bias its shows the specialty of voltage regulation, it must be noted that in fig given below.