Applications of zener diodes voltage regulator, meter. Zener diode can work as a voltage regulator if it is introduced in a circuit. Todays most commonly used diode is semiconductor diode. With 2 v across a 400 ohm resistor, the current through that resistor and the diode, in series is 5 ma. A zener diode is a silicon semiconductor device that permits current to flow in either a forward or reverse direction. Zener diodes are normal pn junction diodes operating in a reverse biased condition.
A zener diode is a pn junction that has been specially made to have a reverse voltage breakdown at a specific voltage. This represents the maximum amount of power the zener current can dissipate. The zener diode working principles and its various. It is because multimeters usually do not have enough input voltage to put the zener into breakdown region. Zener diode operation the zener diode operates just like the normal diode when in the forwardbias mode, and has a turnon voltage of between 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. 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 and remains nearly constant even with. Zener diode a zener diode is designed to operate in the breakdown mode. Understanding the differences between a zener diode and a junction diode is crucial.
However, when connected in the reverse mode, which is usual in most of its applications, a small leakage current may flow. Zener voltage regulation with temperature zener diodes are affected by temperature changes associated with their voltage temperature coefficient. The zener diode utilises the same basic structure as an ordinary diode, but the concept of operation of the reverse breakdown effects are not normally wanted or used for normal diode operation. Applications of zener diodes zener diodes finds a wide applications commercially and industrially. However, the major disadvantage of such a power supply is that the output voltage changes with the variations in the input voltage or load. Zener diode as a voltage regulator working principles. The zener diode since a zener diode is usually operating in the breakdown or. Zener diodes are manufactured to operate reliably and quite precisely in this region, recovering fully.
A zener diode is heavily doped to reduce the reverse breakdown voltage. In our previous articles, we explain in detail about diodes, pn junction diode, semiconductors etc. The reverse breakdown region is the vi characteristic of zener diode above zener breakdown voltage. Currentvoltage characteristic of a zener diode with a breakdown voltage of 17 volt. 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 diode clipper, also known as a diode limiter, is a wave shaping circuit that takes an input waveform and clips or cuts off its top half, bottom half or both halves together. Zener diode as voltage regulator tutorial electronicstutorials. Zener diode operation and applications ece tutorials. The nominal operation voltage of a zener diode is also known as the breakdown voltage of the zener diode, depending on the application for which the diode is to be used, this is often the most important criteria for zener diode selection. The operation of these diodes is normal as pn junction diodes but at the time of transient voltage its operation changes. Types of diodes small signal, led, schottky, zener. The forward characteristics of zener diode are similar to that of normal pn junction diode. In our previous articles, we explain basic theory of semiconductors, pn junction diode, and pn junction diode characteristics etc. Zener diode made specially to operate in the reverse breakdown region.
When forward biased voltage is applied to the zener diode it allows large amount of electric current and blocks only a. In the circuit shown below, the zener diode is ideal and zener voltage is 6 v. The vi characteristics of a zener diode is as shown in the figure below. A main difference between zener diodes and regular silicon diodes is the way they are used in the circuits. The diode the diode is a two terminal semiconductor device that allows current to flow in only one direction. This clipping of the input signal produces an output waveform that resembles a flattened version of the input.
Operation of zener diode voltage regulator instrumentation. 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. Diode is an electronic device conduct current in one direction i. Zener diodes are normally used only in the reverse bias direction. In normal condition the impedance of the diode is high. In this tutorial, we will examine the use of zener diode in pspice and learn about editing the properties of devices this tutorial is written with the assumption that you know how to do all of the basic things in. For this reason, they are also referred to as voltageregulator diodes. They can also be used in other circuits apart from just providing a voltage reference. The basic diagram of zener diode as voltage regulator is given below. Because of its unusual properties it fills a longstanding need in electronic circuitry.
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. The active portion of a zener diode is a semiconductor pn junction. Operation of zener diode voltage regulator engineering. Zener diode is reverse biased during its operation. The zener diode is used in its reverse bias or reverse breakdown mode, i. Pdf explain a little about the zener diode sina taherinasab. Diodes and diode circuits tlt8016 basic analog circuits 20052006 11 3. 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.
Ee40 lec 18ee40 lec 18 diode circuitsdiode circuits. It provides, among other useful functions, a constant voltage reference. Switching diodes switching diodes, sometimes also called small signal diodes, are single diodes in. In the circuit above, there is 10 v across the zener diode, and 2 v across the resistor. The vast majority of all diodes are the pn diodes found in cmos integrated circuits, which include 2 diodes per pin and many other internal diodes. 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. 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. Several stabilising circuits have been designed but only zener diode as a voltage stabiliser.
As we know if the voltage across the diode exceeds a certain value it would draw excessive current from the supply. Zener diodes acts like normal pn junction diodes under forward biased condition. Notice the change of voltage scale between the forward biased positive. It is constructed of a p and an n junction connected together. This was a bad thing before the whole avalanche breakdown, large current. The zener diode is connected with its cathode terminal connected to the positive rail of the dc supply so it is reverse biased and will be operating in its. Types, operation and symbols guide analyse a meter. The materials and applications of the two major types of diodes studied in this lab are found in table 3 below.
Some of the important applications of a zener diodes are as a voltage regulator or stabilizer, as a meter protector and as a wave shaper. When any transient voltage occurs in the circuit the diode enters in to the avalanche breakdown region in which the low impedance is provided. The operation of a zener diode is alike normal diode in forward biased mode. The circuit shown on figure 1a will be used to explore the characteristics of operation in the breakdown region. In this article, we are going to explain zener diode and its applications in detail. Operation of zener diode voltage regulator a rectifier with an appropriate filter serves as a good source of d. Explain how normal diodes might be used as crude substitutes for a zener diode in the following circuit. In breakdown the voltage across the zener diode is close to constant over a wide range of currents thus making it useful as a shunt voltage regulator. Zener diode working, characteristics and application as. 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. A zener diode is a type of diode that allows current to flow in the conventional manner from its anode to its cathode i. The zener diode structure is optimised to ensure the required performance this entails some differences to the structure of an ordinary diode.
There are many circuits that use zener diodes, ranging from very simple zener diode circuits, up to far more complicated ones. Zener diodes are silicon diodes specifically constructed to operate in what is known as the breakdown region. The iv characteristic curve of the diode is shown on. Hbd854 zener theory and design considerations handbook. Its characteristics are otherwise very similar to common diodes. The zener diode of zener voltage vz is reverse connected across the. The symbol of zener diode is shown in the figure below. A zener diode can be used as a voltage regulator to provide a constant voltage from a source whose voltage may vary over sufficient range. Application of zener diode as we have gone through the first part of the article we know what is zener diode and what is the basic principle of operation of it. Zener diodes cannot be tested individually with a multimeter. Diode operation no current flows because the holes and electrons are moving in the wrong direction.
However, a zener shows variation from a normal diode in the aspect of its doping concentration. Many types of diode are used for a wide range of applications. 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. Here we are going to explain about diodes and its types. Here with the applied voltage, the voltage across the zener. A zener diode is a type of diode that allows current to flow in the conventional manner from its. Diode type rectifier diode zener diode material silicon silicon voltage range v br to 1.
Since the actual voltage available from a given zener diode is temperature dependent, it is necessary to determine. A zener diode is a special type of device designed to operate in the zener breakdown region. The fixed voltage property of zener diodes makes them extremely handy as quick voltage references. The maximum voltage rating specifies how much reverse voltage a diode can withstand before breakdown occurs. That means a large majority current flows through the device when the forward potential is applied to it. Zener diodes or voltage reference diodes are used in a variety of circuits to enable them to provide a voltage reference. Zener diodes are designed to operate in the reverse breakdown region and circuits containing them provide voltage regulation or voltage referencing. 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. As mentioned earlier, the characteristics of the zener diode make it ideal for application as a voltage regulator. For example, the halfwave rectifier is a clipper circuit. An ordinary diode operated in this region will usually be destroyed due to excessive current.
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