They are also called pn diodes in analogy with vacuum diodes. 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 or voltage reference diodes are used in a variety of circuits to enable them to provide a voltage reference. Please take note of the zener diodes orientation in the above circuit. Example zener diode circuit analysis blank ku ittc. The zener diode has a normal forward characteristic where the current rises after the initial turnon voltage is reached. The voltage developed across resistor r 1 trigger transistor t 1 as a result it provides base current to transistor t 2.
These include small signal diodes, zener diodes, light emitting diodes, schottky diodes, tunnel diodes, avalanche diodes, etc. Nptel video lectures, iit video lectures online, nptel youtube lectures. Explain how normal diodes might be used as crude substitutes for a zener diode. This reverse breakdown called zener breakdown occurs very sharply. Pdf be8251 basic electrical and electronics engineering. During the negative alternation, the zener acts as a forwardbiased diode. Reverse biasing a pn junction can lead to avalanche or zener breakdown. Working of the zener diode is similar to a pn junction diode in forward biased condition, but the. Zener diodes are normal pn junction diodes operating in a reverse biased condition.
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. Gate 2011 electronics and communication engineering set c. They can also be used in other circuits apart from just providing a voltage reference. Operation of zener diode voltage regulator engineering. A zener diode, when used in voltage stabilization circuits, is biased in a reverse bias region below the breakdown voltage b reverse breakdown region c forward bias region d forward bias constant current mode. Below figures shows three basic ways the limiting action of a zener diode can be used. Zener diode examples and circuit analysis book pdf by. 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.
The reverse breakdown of a pn junction may occur either due to zener effect or avalanche effect. The pn junction is a versatile element, which can be used as a. Nptel mechanical mechatronics and manufacturing automation. There are many circuits that use zener diodes, ranging from very simple zener diode. Such junctions show a pronounced rectifying behavior. Diodes zener diodes photodiodes optical isolation application. The relationship is obtained by applying kvl and it is vs vg r im. Introduction to basic electronics, electronic devices, semi conductor diodes, wave shaping using diodes, zener diode characteristics, transistor biasing, hparameters.
Zener diode breaks down and stops the voltage to pass to the next circuit. Pn junction diode multiple choice questions answers. 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. Zener diode as a voltage regulator, rectificationhalf wave rectifier, full wave rectifier, bridge rectifier.
Pn junctions consist of two semiconductor regions of opposite type. 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 section consists of both the expected and measured experiment results of the zener and regulator power supplies. Lecture 10 zener regulator and voltage regulator youtube. 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. User may specify either, both, or neither of the at least and no more than. The value of this current is given in the data sheet for d. 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. Part a shows a zener used to limit the positive peak of a signal voltage to the selected zener voltage. 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. Zener diodes diodes that can be made to conduct backwards.
Basic diode electronics introduction to diodes the pn junction the pn junction is a homojunction between a ptype and an ntype semiconductor. The data sheet states that the zener voltage is 12 v however here i have about 12% discrepancy. The zener voltage is probably better seen as the break down voltage for the reversebiased zener diode. Special types of diodes called zener diodes are designed to operate in the zener breakdown region. Types of diodes small signal, led, schottky, zener. Outline diode iv characteristics diode approximations rectifier circuits voltage regulators clamp and limiting circuits 2.
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. Diodes and transistors university of california, berkeley. Terry sturtevant electronics zener diodes and photodiodes. In a zener diode voltage regulator circuit,the source series resistance rs 20 ohm. Basic electronics video lectures nptel engineering video. 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. Zener diode characteristics video lecture by prof t. When transistor t 2 is on, the relay rl 1 get energized and the voltmeter gets connected across the zener diode. Zener diodes can be used in ac applications to limit voltage swings to desired levels. Zener diode has the property of behaving like a dc battery in on state i. If you impress a higher voltage on it, it will collapse from the applied voltage and allow. Pn junction failure below 5 v is caused primarily by. In this tutorial, we will learn about different types of diodes. It could be with a voltage source corresponding to vz which is the beak down voltage and a series resistance rz.
Highreliability discrete products and engineering services since 1977 1n7461n759 silicon planar zener diodes rev. Diode behavior forward bias exponential behavior reverse bias breakdown controlled breakdown. Zener voltage v z is the reverse voltage at which breakdown occurs in a zener diode search logic. Zener diode circuit analysis consider the circuit below. Communication engineering to meet industrial and social requirements with ethical responsibility. Basic electronics notes on vi characteristics of zener. 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.
If source voltage vs can vary from 20 volt to 30 volt,find the maximum and minimum current in the diode. The large amount of current that will then flow could destroy the diode. Clipping calculating resistance zener diodes the zener diode will conduct in reverse bias once the voltage exceeds the zener. A wide variety of diodes is available, with vbr ranging from a few volts. 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. Breakdown voltage 20 v but zener breakdown voltage 5 v zener diode zener diodes. This effect, called zener breakdown, occurs at a precisely defined voltage, allowing the diode. Chitralekha mahanta from iit guwahati made available by nptel. Department of electronics and communication engineering. Basic electronics and lab online course video lectures by iit madras. When the zener diode to be tested is connect across probes, a voltage is developed across resistor r 1.
A typical zener diode voltagecurrent characteristic is shown in. Several stabilising circuits have been designed but only zener diode as a voltage stabiliser. Introduction to diodes university of california, san diego. Semiconductor diodes semiconductor materials intrinsic and extrinsic types ideal diode terminal characteristics of diodes. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. Zener diode is a reversebiased heavilydoped pn junction diode which operates in the breakdown region. This will be a brief note on different types of diodes with basic functionality and its circuit symbol.
The zener diode working principles and its various. Department of mechanical engineering zener diode regulator r must be small enough that the current through d keeps d in reverse breakdown. Lecture series on electronics for analog signal processing i by prof. Introduction to basic electronics, electronic devices, semi conductor diodes, wave shaping using diodes, zener diode characteristics, transistor biasing. 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.
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