By using an led and a zener diode we can create a circuit which gives turns on. Thus the load voltage remains at constant by altering the current flow through the zener diode. You will see a rigorous analysis of semiconductors. Zener diode as a voltage regulator zener diode is a silicon semiconductor with a pn junction that is specifically designed to work in the reverse biased condition. Diodes in the first lecture, we discussed linear circuit components resistors, capacitors, and inductors. For zener diodes, silicon is preferred to ge because of its high temperature and. Use the diode equation for that state to solve the circuit equations and find i d and v d 3.
Notice the change of voltage scale between the forward biased positive. The vi characteristics of a zener diode can be divided into two parts i forward characteristics. Such junctions show a pronounced rectifying behavior. In fact, zener diodes are designed to operate in this region. Basics currentvoltage characteristic of a zener diode with a breakdown voltage of 17 volt. Basic electronics notes on vi characteristics of zener.
They are also called pn diodes in analogy with vacuum diodes. Zener effect dominates at reverse voltages less than 5 volt whereas avalanche effect dominates above 5 v. The pn junction is a versatile element, which can be used as a. The reverse breakdown of a pn junction may occur either due to zener effect or avalanche effect. This was a bad thing before the whole avalanche breakdown, large current. Even silicon has entered the quantum mechanical domain. In terms of water models, it can be thought of as a oneway. Whites, ee 320 lecture 6 page 2 of 11 provided that the power dissipated in the diode is less than the maximum rated, the diode is not damaged when operating in the breakdown region.
Currentvoltage characteristic of a zener diode with a breakdown voltage of 17 volt. When forward biased, it behaves like a normal signal diode, but when the reverse voltage is applied to it, the voltage remains constant for a wide range of currents. When the diode is passing current we say it is forward biased. Diode is reverse biased when vanode diode conducts current very weakly typically diode current is almost independent of voltage, until breakdown effective resistance impedance of diode is very large currentvoltage relationship for a diode can be expressed as. Essentially, it allows an electric current to flow in one direction, but blocks it in the opposite direction. Voltage regulation using zener diodes bryan witherspoon november 8, 2008 abstract in digital or mixedsignal applications, there is a need to precisely regulate the voltage entering or exiting a circuit. The pn junction diode the negative terminal of the biasvoltage source pushes the conductionband electrons in the n region toward the pn junction, while the positive terminal pushes the holes in the p region toward the pn junction when it overcomes the barrier potential v b, the external voltage source provides the n region electrons with enough energy to penetrate the. As a result zener diode circuits are often used in power supplies when regulated outputs are needed. Diodes we start our study of nonlinear circuit elements. A brief description of how semiconductor devices work is rst given to understand their i v characteristics. The circuit schematic symbol of a diode is shown in figure 5.
The zener diode working principles and its various. Working of the zener diode is similar to a pn junction diode in forwarding biased condition, but the uniqueness lies in the fact that it can also conduct when it is connected in reverse bias above its thresholdbreakdown voltage. A diode can be defined as the fundamental electronic component that allows the flow of electricity in one direction only. Zener diodes acts like normal pn junction diodes under forward biased condition. Ee40 lec 18ee40 lec 18 diode circuitsdiode circuits. A zener diode is like a normal silicon diode, where a forward biased diode will pass current with a 1 volt drop. 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 pn junction diode a semiconductor diode consists of an n material region and a p material region separated by a pn junction the n region has many conduction electrons the p region has many holes as a result of recombination, a large number of positive in the n region and negative in the p region ions builds up near the. Zener diode examples and circuit analysis book pdf by. Zener diodes the simplest of all voltage regulators is the zener diode voltage regulator. It means that a zener diode can be used as an alternate current path. Write down all circuit equations and simplify as much as possible 2.
Semiconductor diodes the diode is the simplest type of semiconductor device. The iv characteristics of a zener diode and the corresponding constantvoltage model are shown below. Zener diode voltages as well as producing a single stabilised voltage output, zener diodes can also be connected together in series along with normal silicon signal diodes to produce a variety of different reference voltage output values the values of the individual zener diodes can be chosen to suit the application while the silicon. Note that in the forward bias condition a zener diode is still a diode and when the ac waveform output goes negative below 0. Pdf be8251 basic electrical and electronics engineering. Zener diode as a voltage regulator working principles. These elements diodes and transistors are made of semiconductors. A simple zener diode voltage regulator in the voltage regulator the zener diode operates in the breakdown region, which ensures approximately constant voltage across it. Diode water model if a voltage source is oriented in a circuit so that the intended current. Varactor diode is a pn junction diode whose capacitance is varied by varying the reverse voltage. The diodes are classified into different types based on their working principles and characteristics.
Piv is the peakinversevoltage of the diode forward bias occurs when the ptype block is connected to the positive terminal of the battery and the ntype is connected to the negative terminal of. Oct 12, 2016 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 circuit. The rated vz at the specified izt is listed for these zener diodes. 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 voltage or zener voltage. Zener diode is on when it operates on the zener region, i. The zener diode is a form of semiconductor diode that is widely used in electronics circuits as a voltage reference. Diode behavior forward bias exponential behavior reverse bias breakdown controlled breakdown. Ahmed power diodes characteristics a power diode and thyristor devices are most important in different power electronic converter topologies. Zener diode as voltage regulator tutorial electronicstutorials. On a special case, this article discuss about gunn. Zener diode made specially to operate in the reverse breakdown region. Recipe for solving diode circuits state of diode is unknown before solving the circuit 1. They can also be used in other circuits apart from just providing a voltage reference. The zener diode has a unique property that offers a simple, lowcost solution to this problem.
Maximum reverse voltage potential that can be applied before entering the zener region is called the peak inverse voltage piv or peak reverse voltage prv. A diodes iv characteristic is shown in figure 6 below. Special diodes zener diodes diodes and diode circuits. The constant vz developed across the diode can then be applied to a load. The breakdown voltage of a zener diode can be set by controlling the doping level. Zener diodes or voltage reference diodes are used in a variety of circuits to enable them to provide a voltage reference. Zener diodes are rated by their breakdown voltage v z and maximum power p z typically 400mw or 1. Zener diode is a reversebiased heavilydoped pn junction diode which operates in the breakdown region. With 2 v across a 400 ohm resistor, the current through that resistor and the diode, in series is 5 ma. Zener diode definition, vi characteristics, and breakdown. When forward biased voltage is applied to the zener diode it allows large amount of electric current and blocks only a small amount of electric current. The zener diode is used in its reverse bias or reverse breakdown mode, i.
Varactor diode definition, symbol, construction and. Zener diode examples and circuit analysis book pdf by alvin. 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 circuit. For the zener diode we are using a model with a breakdown voltage vz and an. These include generic diode, schotty diode, shockley diode, constantcurrent diode, zener diode, light emitting diode, photodiode, tunnel diode, varactor, vacuum tube, laser diode, pin diode, peltier diode, gunn diode, and so on. The relationship is obtained by applying kvl and it is vs vg r im. A zener diode is a special type of device designed to operate in the zener breakdown region. Diode applicationszener diode zener diode zener diode operates in reverse bias rb at the zener voltage v z. Electronic devices chapter 3 special purpose diodes the zener diode a major application for zener diodes is as a type of voltage regulator for providing stable. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal.
The zener diode working principles and its various applications. Varactor diode is also sometimes referred to as varicap diode, tuning diode, variable reactance diode, or variable capacitance diode. There are many circuits that use zener diodes, ranging from very simple zener diode circuits, up to far more complicated ones. Regulator zener diode regulator for low current power supplies a simple voltage regulator can be made with a resistor and a zener diode connected in reverse. Diodes and diode circuits tlt8016 basic analog circuits 20052006 11 3.
Lecture 1 introduction to semiconductors and semiconductor. The zener diode or voltage reference diode is an electronic component that provides a stable and defined 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. When a zener diode is reversed biased, theres a different voltage drop. The varactor diode is manufactured in such as way that it shows better transition capacitance property than the ordinary diodes.
Basic electronics notes on vi characteristics of zener diode in pdf. Hence comparing the schematic symbol to the pn junction in figure 4, we see the anode is the ptype semiconductor and the cathode is the ntype semiconductor. Part 5 large signal complete model and small signal limited use models of a diode reading. Because these zener diodes come with a specific reverse breakdown. Zener diodes are normal pn junction diodes operating in a reversebiased condition. For the zener diode we are using a model with a breakdown voltage vz and an effective resistance rz in the breakdown as shown on figure 2 and illustrated on figure 1. All the diodes that weve been looking at up till this point, if we operate them in reverse voltage they either look like an open circuit or, if you put too much.
Basic electronics notes on vi characteristics of zener diode. Diodes and transistors university of california, berkeley. Diode schematic symbol and actual picture of a common 1n914 diode the black stripe in the picture is the cathode. A zener diode is much like a standard diode in many respects, except that it is designed to operate in and notice here the reverse breakdown region of its operating curve. Basic diode electronics introduction to diodes the pn junction the pn junction is a homojunction between a ptype and an ntype semiconductor. In the circuit above, there is 10 v across the zener diode, and 2 v across the resistor. Diode employing the unique portion of the characteristics of a pn junction is called zener diode. Varactor diode definition, symbol, construction and working. Before going to varactor diode, lets first take a look at the capacitor. 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. Pn junctions consist of two semiconductor regions of opposite type. The resistor value is chosen such that several ma flow through it and through the zener, keeping it in its breakdown region. Diodes in the first lecture, we discussed linear circuit components resistors, capacitors, and inductors we found that we could build some electronic circuits using only these devices however, much of electronics in particular digital electronics depends upon nonlinear devices. Zener diode symbol zener diode circuit zener diode vi characteristics zener diode working zener diode applications faqs.
Difference between avalanche breakdown and zener breakdown. Zener diode a zener diode is designed to operate in the breakdown mode. Basics currentvoltage characteristic of a zener diode with a breakdown voltage of. Zener diodes are designed to operate in the reverse breakdown region. Electrical characteristics tamb 25 c, unless otherwise specified part. It acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator zener diode. When forward biased voltage is applied to the zener diode it allows large amount of electric current and blocks only a. Diodes 2 in simple terms, a diode is a device that restricts the direction of flow of charge carriers electrons in this class 1. What is a zener diode voltage reference electronics notes. University of technology lecture note 3 electrical engineering department power diode characteristics electrical engineering division page 1 of 8 eg 405.