A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. Clipping calculating resistance zener diodes the zener diode will conduct in reverse bias once the voltage exceeds the zener. If you impress a higher voltage on it, it will collapse from the applied voltage and allow. This section consists of both the expected and measured experiment results of the zener and regulator power supplies. The zener diode working principles and its various. Analysis of networks employing zener diodes is quite similar to that applied to the analysis off semiconductor i d t diodes di d iin previous i sections. Lecture series on electronics for analog signal processing i by prof.
Radhakrishna rao, department of electrical engineering,iit madras. Zener breakdown is unlikely to occur in bjts because the doping densities in the base are generally low less than. Zener diodes diodes that can be made to conduct backwards. Introduction to basic electronics, electronic devices, semi conductor diodes, wave shaping using diodes, zener diode characteristics, transistor biasing, hparameters. Department of electronics and communication engineering. Zener diode made specially to operate in the reverse breakdown region. Introduction to diodes university of california, san diego. Explain how normal diodes might be used as crude substitutes for a zener diode. A typical zener diode voltagecurrent characteristic is shown in. During the negative alternation, the zener acts as a forwardbiased diode. Zener diodes or voltage reference diodes are used in a variety of circuits to enable them to provide a voltage reference.
Several stabilising circuits have been designed but only zener diode as a voltage stabiliser. Zener diode examples and circuit analysis book pdf by. Zener diode is a reversebiased heavilydoped pn junction diode which operates in the breakdown region. Pdf be8251 basic electrical and electronics engineering. It could be with a voltage source corresponding to vz which is the beak down voltage and a series resistance rz. Introduction to basic electronics, electronic devices, semi conductor diodes, wave shaping using diodes, zener diode characteristics, transistor biasing. 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. Part a shows a zener used to limit the positive peak of a signal voltage to the selected zener voltage. Zener voltage v z is the reverse voltage at which breakdown occurs in a zener diode search logic. Below figures shows three basic ways the limiting action of a zener diode can be used. Zener diode breaks down and stops the voltage to pass to the next circuit. Note that the load resistor r l is in parallel with the zener diode, so that the voltage v o across this load resistor is equal to the zener diode. Diodes zener diodes photodiodes optical isolation application. Basic electronics notes on vi characteristics of zener.
Communication engineering to meet industrial and social requirements with ethical responsibility. Types of diodes small signal, led, schottky, zener. Breakdown voltage 20 v but zener breakdown voltage 5 v zener diode zener diodes. I did not further increase the voltage source, because i am afraid it will destroy the diode, so is there a better way to measure the zener. If source voltage vs can vary from 20 volt to 30 volt,find the maximum and minimum current in the diode. Zener diode characteristics video lecture by prof t. The value of this current is given in the data sheet for d. Pn junctions consist of two semiconductor regions of opposite type. The voltage developed across resistor r 1 trigger transistor t 1 as a result it provides base current to transistor t 2. This is a complete series of 1 watt zener diode with limits and excellent operating characteristics that reflect the superior capabilities of siliconoxide passivated junctions.
Chitralekha mahanta from iit guwahati made available by nptel. The data sheet states that the zener voltage is 12 v however here i have about 12% discrepancy. When the zener diode to be tested is connect across probes, a voltage is developed across resistor r 1. Nptel video lectures, iit video lectures online, nptel youtube lectures. In a zener diode voltage regulator circuit,the source series resistance rs 20 ohm. Semiconductor diodes semiconductor materials intrinsic and extrinsic types ideal diode terminal characteristics of diodes. The relationship is obtained by applying kvl and it is vs vg r im. Lecture 10 zener regulator and voltage regulator youtube. Zener diode circuit analysis consider the circuit below. Zener diode has the property of behaving like a dc battery in on state i. 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.
Basic electronics video lectures nptel engineering video. Terry sturtevant electronics zener diodes and photodiodes. In this tutorial, we will learn about different types of diodes. 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. Special types of diodes called zener diodes are designed to operate in the zener breakdown region. The large amount of current that will then flow could destroy the diode. Diodes and transistors university of california, berkeley. The reverse breakdown of a pn junction may occur either due to zener effect or avalanche effect. Pn junction failure below 5 v is caused primarily by. This will be a brief note on different types of diodes with basic functionality and its circuit symbol.
Such junctions show a pronounced rectifying behavior. There are many circuits that use zener diodes, ranging from very simple zener diode. Gate 2011 electronics and communication engineering set c. Pn junction diode multiple choice questions answers.
Zener diode is a pn junction diode specially designed for operation in the breakdown region i special purpose diodes questions and answers pdf free download for electronics engineering. Operation of zener diode voltage regulator engineering. Zener diodes can be used in ac applications to limit voltage swings to desired levels. 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. This effect, called zener breakdown, occurs at a precisely defined voltage, allowing the diode. Outline diode iv characteristics diode approximations rectifier circuits voltage regulators clamp and limiting circuits 2. Example zener diode circuit analysis blank ku ittc.
The zener voltage is probably better seen as the break down voltage for the reversebiased zener diode. This reverse breakdown called zener breakdown occurs very sharply. The zener still conducts electricity in the forward direction like any other diode, but also conducts in the reverse direction, if the voltage applied is reversed and larger than the zener. 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. Department of mechanical engineering zener diode regulator r must be small enough that the current through d keeps d in reverse breakdown. User may specify either, both, or neither of the at least and no more than. The schematic symbol for a zener diode is shown above it is very similar to that of a regular diode, but with bent edges on the bar. Reverse biasing a pn junction can lead to avalanche or zener breakdown. Nptel mechanical mechatronics and manufacturing automation. Basic diode electronics introduction to diodes the pn junction the pn junction is a homojunction between a ptype and an ntype semiconductor. These include small signal diodes, zener diodes, light emitting diodes, schottky diodes, tunnel diodes, avalanche diodes, etc.
Highreliability discrete products and engineering services since 1977 1n7461n759 silicon planar zener diodes rev. Zener diode as a voltage regulator, rectificationhalf wave rectifier, full wave rectifier, bridge rectifier. The pn junction is a versatile element, which can be used as a. When transistor t 2 is on, the relay rl 1 get energized and the voltmeter gets connected across the zener diode. Basic electronics and lab online course video lectures by iit madras. It acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator zener diode. Working of the zener diode is similar to a pn junction diode in forward biased condition, but the. A wide variety of diodes is available, with vbr ranging from a few volts. They can also be used in other circuits apart from just providing a voltage reference. Zener diodes are normal pn junction diodes operating in a reverse biased condition. They are also called pn diodes in analogy with vacuum diodes. Diode behavior forward bias exponential behavior reverse bias breakdown controlled breakdown. Please take note of the zener diodes orientation in the above circuit. The zener diode has a normal forward characteristic where the current rises after the initial turnon voltage is reached.
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