The pn junction diode is used for rectification purpose because it allows the current to flow only in one direction. Pn junction is not properly doped to control reverse breakdown. 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. The forward bias characteristic of zener diode is same as the normal pn junction diode but in reverse bias it has different characteristic. A normal diode will be permanently damaged for a large reverse current, but a zener diode will not. The schottky diode is a semiconductor also known as hot carrier diode. At the present time, zener diodes use silicon as the basic material in the. Diode can conduct current only in one direction, whereas zener diode allows the conduction in both directions. From the above, it follows that zero power dissipation occurs in an ideal diode.
A perfect diode is a device that only allows current to flow through it in one direction, i. Draw the reverse characteristics of zener diode and determine its break down. Vi characteristics of zener diode vi characteristics of. We operate a zener diode in reverse biased conditions, and this diode does not get damaged even when the voltage across this exceeds the reverse breakdown voltage. The name zener diode was named after the american physicist clarance melvin zener who discovered the zener effect. The pn junction biasing the pn junction the diode trouble shooting. A special type of pn junction diode that operates in reverse biased condition, more specifically in breakdown region is known as zener diode. The symbol of zener diode is similar to the normal p n junction diode, but with bend edges on the vertical bar. Zener diode is a p n junction diode specially designed for operation in the breakdown region in. Using this process for silicon diodes produces two differently doped layers of silicon, which form a pn junction. They are also called pn diodes in analogy with vacuum diodes. According to the diode equation here, the current through a forwardbiased pn junction is proportional to e raised to the power of the forward voltage drop. The zener diode is a particular type of diode that solves this problem. The active portion of a zener diode is a semiconductor pn junction.
The zener diode is a silicon pn junction devices that differs from rectifier diodes because it is designed for operation in the reverse breakdown region. Such junctions show a pronounced rectifying behavior. 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. It has a particular voltage known as break down voltage, at which the diode break downs while reverse biased. These types of diodes are commonly known as zener diodes and are discussed in a later tutorial. Zener diode is a reverse biased heavily doped semiconductor silicon or germanium pn junction diode, which is operated exclusively in the breakdown region. Nonideal pn junction diodes engineering libretexts. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. The diode has two terminals called a cathode and an anode. A pn junction diode is formed when a ptype semiconductor is fused to an ntype semiconductor creating a potential barrier voltage across the diode junction the effect described in the previous tutorial is achieved without any external voltage being applied to the actual pn junction resulting in the junction being in a state of equilibrium. The types of break down diodes include schottky diode, zener diode and avalanche diode. Amount of doping for p and n semiconductor layers are different in the two devices.
A pn junction is the simplest form of the semiconductor diode. A zener diode is a pn junction semiconductor device designed to operate in the reverse breakdown region. A diode which exhibits the zener effect is called a zener diode. Zener diode is a p n junction diode specially designed to operate in the reverse biased mode. A p n junction diode, ddp figure 1 p n junction diode between vddl and vddp therefore, when vddl ramps up first, the, to the powerup sequence. It is a type of switch which only allows the forward current to pass through it. It is made by doping both p and n sides of the junction heavily. Among these are the widely used techniques known as alloying and diffusion which are utilized in fabricating zener pn junctions to provide excellent control over zener breakdown voltage.
We have also learned about diffusion current, depletion region. The current in the pn junction diode can only flow from one side to the other. Semiconductor pn junction diodes physically, diodes are formed by the interface between two regions of oppositely doped semiconductor i. Hbd854 zener theory and design considerations handbook. Pn junction diode applications pn diode applications. The zener and avalanche breakdown both occur in diode under reverse bias. In ideal conditions, this pn junction behaves as a short circuit when it is forward biased, and as an open circuit when it is in the reverse biased. An ideal pn junction diode is based on the following basic assumption. As shown in the figure, pn junction diode is a 2 terminal polarity sensitive device. Diodes and diode circuits tlt8016 basic analog circuits 20052006 4 3. Semiconductor, silicon, pn junction, forward bias, reverse bias, diode. The avalanche breakdown occurs because of the ionisation of electrons and hole pairs whereas the zener diode occurs because of heavy doping.
It is acting as normal diode while forward biasing. Semiconductor diode questions and answers pdf free download mcqs interview objective type questions for eee ece electronics students semiconductor diode. Zener diode is a pn junction diode specially designed to operate in the reverse biased mode. Pn junctions consist of two semiconductor regions of opposite type. Zener diodes are specifically doped, being able to transmit current in both directions. Pn junction diode and diode characteristics electronicstutorials. This p n diode applications are very useful for beginners. The behaviour of the pn junction with regards to the potential barriers width produces an asymmetrical conducting two terminal device, better known as the pn junction diode. A simplified planar silicon diode is illustrated in fig. In our previous articles, we explain in detail about diodes, pn junction diode, semiconductors etc. Semiconductor pnjunction diodes physically, diodes are formed by the interface between two regions of oppositely doped semiconductor i. Zener diode lab viva questions and answers pdf free download.
The reverse current in a photodiode is directly proportional to the intensity of light falling on its pn junction. 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. If two electrodes are connected to the opposite sides of a pnjunction, it becomes a diode. Difference between pn junction diode and zener diode. Diode is an electronic component that allows the flow of electricity in one direction without resistance or with very little resistance while in the opposite direction has. P n junctions consist of two semiconductor regions of opposite type.
Once that happens, large current flows through the junction and the diode may get destroyed. A photodiode is a reversebiased silicon or germanium pn junction in which reverse current increases when the junction is exposed to light. Zener designed a p n junction diode in reverse bias to operate in the breakdown region. Because this is an exponential function, current rises quite rapidly for modest. Zener diode experiment viva questions with answers characteristics mcqs interview questions. Pn junction diode plays a vital role in our electronic fields, because of their unique property current flows in only one direction they are used in many electronic or electrical circuits like rectifiers, switches, clippers, clampers, voltage multipliers in this article, we will learn about what is a pn junction diode and how it works and also effect on pn junction diode with different. Exp3 h3characteristics of pn diode and zener diode free download as pdf file. Zener diode working, characteristics and application as.
Difference between diode and zener diode compare the. Undoped or intrinsic silicon has a lattice structure of atoms, each having four valence electrons, but p type silicon and. Pn junction diode and zener diode pn junction diode. Pn junction diodes are made of two p and n semiconductor layers, permitting current to flow in only in one direction, thus being used as rectifiers. Pn junction diode and its characteristics in chapter 1 understanding the pn junction, we have seen how a pn junction is formed from a ptype and ntype semiconductor. 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. A special type of pn junction diode that operates in reverse biased mode, more specifically in breakdown region is known as zener diode the doping level of the zener diode is somewhat higher than the normal pn junction diode. The region around the junction from which the mobile charge carriers electrons and holes are depleted is called as depletion region. Overview the most important device is a junction between a ptype region and an ntype region when the junction is first formed, due to the concentration gradient, mobile. The doping level of the zener diode is somewhat higher than the normal pn junction diode so that it can provide a sharp breakdown voltage. Zener diode is properly doped to control reverse breakdown. A zener diode is a special diode that is optimized for operation in the breakdown region. Semiconductor diode questions and answers pdf free download posted on august 19, 2018 march 20, 2017 by engineer 2 comments posted in semiconductor diode questions. The zener diode working principles and its various.
A p n junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. The diode consists of a special, heavily doped pn junction, designed to conduct in the reverse direction when a certain specified voltage is. In this article, we are going to explain zener diode and its applications in detail. Here you will learn, how the zener diode is used in reverse biasing. Difference between p n junction diode and zener diode. Exp3 h3characteristics of pn diode and zener diode pn junction. Forward bias current flows reverse bias no current flow. In zener diode, electric current flows from both anode to cathode and cathode to anode.
The zener diodes have been designed to operate at voltages ranging from a few volts to several hundred volts. This means that greater the intensity of light falling on the pn junction of photodiode. Definition, symbol, and types of diodes electrical4u. Pn junction diode, characteristics and applications 2020. On the other hand, the zener diode allows both the forward and reverse current to pass through it. Due to heavily doped, its depletion layer is very thin and is order of micrometer. Pn junctions are formed in various kinds of semiconductor devices by several techniques. Zener diodes the simplest of all voltage regulators is the zener diode voltage regulator. If both sides of the junction are heavily doped, it becomes a zener diode, where electrons can tunnel through the bandgap without causing damage to the device. Hence it is defined as a reverse biased heavily doped pn junction diode which operates in breakdown region. The major difference between pn junction and the zener diode is that the pn junction diode allows current to pass only in the forward direction. Zener breakdown and avalanche breakdown the avalanche breakdown and zener breakdown are two different mechanisms by which a pn junction breaks. Zener diode characteristics in the forward region, the zener diode acts like a regular silicon diode, with a 0.
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