Working of a pn junction current iv characteristic of reverse bias a pn junction diode. If the pside anode is connected to the positive terminal of the supply and the nside cathode to the negative terminal of the supply. Currentvoltage characteristics and detailed carrier actions in a pn junction diode. 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. When revrese voltage is increased beyond a value,called breakdown voltage,the reverse current increases sharply and the diode shows almost zero resistance. How a pn junction formed in a diode engineering tutorial. An attractive animation is presented in this video with complete voice description. Before going to the working, i would like to explain how exactly the junction diode is made. A pn junction aggregates the recombination, generation, diffusion and drift effects described in the previous pages into a single device. The pin diode consists of heavily doped p and n regions separated by an intrinsic i region, as shown in figure a. Zener diodes are normal pn junction diodes operating in a reverse biased condition. Rather than a pn junction, there is a metaltosemiconductor junction, as shown in below figure.
Apart from the basic working of the diode, this video also explains vi characteristics and applications of diode rectification using bridge rectifier with help of animation. The photon energy is equal to the energy gap between these two energy levels. There is a small voltage drop across the diode terminals when current flows through a diode. A pn junction diode is a twoterminal electronics element, which can be classified as either. In a ptype semiconductor, the number p p of holes is much larger than the number of electrons n p p p n p. Doping with acceptor creates p type semiconductor while doping with donors produces n type. Diodes what are diodes pn junction forward bias reverse bias zener diodes duration. We have also learned about diffusion current, depletion region. Laser light is monochromatic, which means that it consists of a. Basic electronics optoelectronic diodes tutorialspoint. Holes are the majority carriers and electrons are the minority carriers. Animation how a p n junction semiconductor works forward.
Laser diode working principle a laser diode, or ld also known as injection laser diode or ild, is an electrically pumped semiconductor laser in which the active laser medium is formed by a pn junction of a semiconductor diode similar to that found in a lightemitting diode. When the conventional diode is reverse biased, the depletion region starts expanding and the current starts flowing due to minority charge carriers. 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 depletion region as explained previously with the diode is the area around the pn junction where the electrons from the ntype silicon, have diffused into the holes of the ptype material. One electrode of the semiconductor device is termed the anode and the other is termed the cathode. Jul 09, 2016 tunnel diode working principle a tunnel diode or esaki diode is a type of semiconductor that is capable of very fast operation, well into the microwave frequencyregion, made possible by the use of the quantum mechanical effect called tunneling. Pn junction, types, construction and working power. Dec 26, 2016 an attractive animation is presented in this video with complete voice description. In a small silicon diode operating at its rated currents, the voltage drop is. When forwardbiased, it acts like a currentcontrolled variable resistance. Schottky diode working principle engineering tutorial. The light is made to incident on maximum area possible with thin glass on the top so as to collect maximum light with minimum resistance. However if the diodes terminals are shorted together, a few holes majority carriers in the ptype material with enough energy to overcome the potential barrier will move.
Find materials for this course in the pages linked along the left. The quantum theory says that when the electron comes down from the higher energy level to the lower energy level then, the energy emits from the photon. A diode s working principle depends on the interaction of ntype and ptype semico nductors. Apr 07, 20 when revrese voltage is increased beyond a value,called breakdown voltage,the reverse current increases sharply and the diode shows almost zero resistance. For example, a common type of transistor, the bipolar junction transistor, consists of two pn junctions in series, in the form n pn or pn p. For a current to flow across the pn diode junction it must be forward biased. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. May 28, 2017 ive tried to make this explanation as simple as possible so that no conceptual doubts arise. Diode working principle and types of diode electrical. The current supply between collector and emitter controlled by the supply signal of base terminal. The diode has two terminals called a cathode and an anode. A laser diode, or ld also known as injection laser diode or ild, is an electrically pumped semiconductor laser in which the active laser medium is formed by a pn junction of a semiconductor diode similar to that found in a lightemitting diode the term laser stands for light amplification by stimulated emission of radiation.
These materials are ntype, having electrons are majority carrier and ptype material, having holes are majority carrier. Pn junction diode is a device made of two semiconductor material joined together with the required amount of impurity. Silicon a single silicon atom consists of fourteen negatively. A ptype has a lot of holes and an ntype lot of electrons. Its working principle is when the diode is reverse biased, small leakage currents pass through the diode, when the. When a diode is connected in a zero bias condition, no external potential energy is applied to the pn junction. To make use of this pn junction diode we have to apply an external dc voltage to it. Pn junctions are formed by joining ntype and ptype semiconductor materials, as shown below. Like any diode, the pn junction diode has two connections or electrodes. When a photon of light is absorbed by one of these atoms in the ntype silicon it will dislodge an electron, creating a free electron and a hole.
But before we can understand how the pn junction works, we must first consider current flow in the materials that make up the junction and what happens initially within the junction when these two materials are joined together. Since the ntype region has a high electron concentration and the ptype a high hole concentration, electrons diffuse from the ntype side to the ptype side. It is the most essential and the basic building block of the electronic device. Real pn junction characteristics, its model and design the characteristics of real pn junction diodes, the charge and capacitance models, and the design strategy. The negative terminal of the battery is connected to the anode of a diode and positive terminal of battery is connected to cathode. A schottky diode, also known as a hot carrier diode, is a semiconductor diode which has a low forward voltage drop and a very fast switching action. Laser diode working principle engineering tutorial. There are so many animated videos available of diode working on. Zener breakdown is caused at very low voltages when compared to the avalanche breakdown. A diodes working principle depends on the interaction of ntype and ptype semico nductors. In other words, we can say that the concentration of free electrons is high and that of holes is very low in an ntype semiconductor. Calculate the ideal diode current assuming that the ntype region is much smaller than the diffusion length with w n 1 mm and assuming a long ptype region.
Definition, symbol, and types of diodes electrical4u. Reverse bias of pn junction when the voltage is applied this way round it tends to pull the free electrons and holes apart, and increases the height of the energy barrier between the two sides of the diode. A pn junction consists of two semiconductor regions with opposite doping type as shown in figure. It will not pass current as readily as a conductor nor will it block current as effectively as an insulator. Dec 16, 2018 in this video, we will explore the inner workings and applications of the diode in great detail. Reverse voltage above 25 v destroys the junction permanentaly. With proper biasing, pn diode allows current to flow in single direction. A schottky junction is a special case of a pn junction, where metal serves the role of the ptype semiconductor.
Here we have explained the forward biased diode using below animation. Diode working with animations electronicselectrical eeecex. A pn junction diode is twoterminal or twoelectrode semiconductor device, which allows the electric current in only one direction while blocks the electric current in opposite or reverse direction. This is the voltage required to reach a flat band diagram and sets an upper limit typically an overestimate for the voltage that can be applied to a diode before it burns itself up. This understanding will lay a better foundation for exploring further into different aspects of semiconductor electronics. N on step by step guidelines for downloading free plc software. Laser diode working principle instrumentation tools. It denotes how a diode can be safely operated in reverse bias. However if the diodes terminals are shorted together, a few holes majority carriers in the ptype material with enough energy to overcome the potential barrier will move across the junction against this barrier potential. Semiconductor principles were unknown to the developers of these early. Jan 16, 2018 pn junction diode is a device made of two semiconductor material joined together with the required amount of impurity. A diode is used to block the electric current flow in one direction, i.
Current limiting reactors are connected in series with the power system essentially to damp the short circuit fault current. Pn junction can basically work in two modes, a battery is connected to the diode oforward bias mode positive terminal connected to pregion and negative terminal connected to n region areverse bias mode negative terminal connected to pregion and positive terminal connected to n region. The working principle of a pn junction diode can be broadly understood under three categories. Impurities are added to it to create a region on one side that contains negative charge carriers electrons, called an ntype semiconductor, and a region on the other side that contains positive charge carriers, called a ptype semiconductor. Pn junction diode is a two terminal device, the characteristics of diode depends on the polarity of the external potential applied to the pn junction diode. Unbiased pn junction, forward biased pn junction and reversed biased pn junction. 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. Note if use relay in any circuit then a diode called as flyback diode must connect with parallel of relay input, this is essential for protection. Nov 29, 2017 pn junction diodes as the name suggests are diodes made up by combining one p type and one n type semiconductor. The pn junction diode is a twoterminal device, which is formed when one side of the pn junction diode is made with ptype and doped with the ntype material. Pn junction objective questions instrumentation tools. The same condition can be obtained in photodiode without applying reverse voltage.
The various layers are labelled as p1, n1, p2 and n2 for identification. If you get any answers wrong, just reread the suggested module or section to find the right answer, and learn more about semiconductor diodes. Tunnel diode working principle instrumentation tools. How a pnjunction diode works university of st andrews. Pn junction optical properties and metalsemiconductor contacts. Diodes explained the basics how diodes work working principle pn junction duration.
In this video, lets explore the famous pn junction. An ntype semiconductor has plenty of free electrons and a very few numbers of holes. The total charge on each side of a pn junction must be equal and opposite to maintain a neutral charge condition around the junction. The pn junction is an interface between a ptype and an ntype region and is used to construct diodes and transistors. Pn junction theory a pn junction is formed when an ntype material is fused together with a ptype material creating a semiconductor diode in the previous tutorial we saw how to make an ntype semiconductor material by doping a silicon atom with small amounts of antimony and also how to make a ptype semiconductor material by doping another. Basic electronics optoelectronic diodes these are the diodes which are operated on light. Similarly, holes flow by diffusion from the ptype side to the ntype side. Semiconductor simulations, animations and java applets. The junction of n and p semiconductors is free of charge carriers. Pn junction diode baising and its vi characteristics. With the increase of reverse voltage, the reverse current also starts increasing. A pn junction diode is made of a crystal of semiconductor, usually silicon, but germanium and gallium arsenide are also used. A diodes working principle depends on the interaction of ntype and ptype.
Pn junction diode construction working and uses electrical. Schottky diode working principle instrumentation tools. Its working principle is when the diode is reverse biased, small leakage currents pass through the diode, when the reverse voltage is further increased the leakage current also. Objective questions on pn junction diode electrical study. A pn junction diode is a two terminal single crystal semiconductor device whose one side is doped with acceptors and other side by donors. This video explains complete process of diode working i. The pn junction diode is the basic semiconductor diode format. Jan 29, 2019 pn junction diode is one of the fundamental elements in electronics. Jul 29, 2016 a simple explanation of the working principle of a diode. The positive terminal of the battery is connected to the anode of a diode and negative terminal to the cathode when battery is not connected, there is a barrier potential of 0.
Named after its inventor, a shockley diode is a pnpn device having two terminals as shown in fig. At the junction, majority carriers diffuse across the junction, and this creates a depletion layer and a barrier potential v barrier across the junction. Hence, this voltage is considered during reverse biased condition. This principle of diode makes it work as a rectifier. We will see what happens when we have a single crystal with a ptype semiconductor on one side and an ntype on the other.
Forward biasing a pn junction diode is very simple. An abrupt silicon pn junction n a 10 16 cm3 and n d 4 x 10 16 cm3 is biased with v a 0. In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity. In this physics digital electronics video lecture in hindi for class 12 we explained forward and reverse bias in pn junction diode in terms of depletion layer and potential barrier. Applying an external dc voltage to the diode is called as biasing. A diode vacuum tube or thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from cathode to plate. Jul 06, 2016 when you take a block of silicon and dope part of it with a trivalent impurity and the other part with a pentavalent impurity, a boundary called the pn junction is formed between the resulting ptype and ntype portions. A diode is a twoterminal electronic component that conducts current primarily in one direction. But ordinary pn junction diode connected in reverse biased condition is not used as zener diode practically. This device acts as a switch and consists of four alternate ptype and ntype layers in a single crystal.
A pn junction diode with an intrinsic material in the deletion region is made to encapsulate in a glass. You just need to take a battery whose values can be varied from o to v volts, connect its positive terminal to the pside of pn junction diode and then connect the negative terminal of battery to the nside of the pn junction diode. A perfect diode is a device that only allows current to flow through it in one direction, i. Apr 05, 2019 in this tutorial, we will learn about pn junction diodes and in particular the characteristics and working of pn junction diode. Working principle of pn junction diode polytechnic hub. Laser diode needs a driver circuit to work properly. As a result it is almost impossible for any electrons or holes to cross the depletion zone and the diode current produced is virtually zero. A semiconductor diode, the most commonly used type today, is a crystalline piece of semiconductor material with a pn junction connected to two electrical terminals. When reversebiased, the pin diode acts like a nearly constant capacitance. Pn junction diodes form the basis not only of solar cells, but of many other electronic devices such as leds, lasers, photodiodes and bipolar junction transistors bjts. The region on the left is ptype with an acceptor density na, while the region on the right is ntype with a. When the diode is forwardbiased, it can be used in led lighting applications.
Since a pregion adjacent to an nregion may be considered a junction diode, the shockley diode is equivalent to. Pn junction diode and characteristics of pn junction diode. Note to those familiar with a diode turn on voltage. A pn junction is the simplest form of the semiconductor diode. A simple explanation of the working principle of a diode. The pn junction is the basis for diodes, certain transistors, solar cells, and other devices. Pn junction diodes as the name suggests are diodes made up by combining one p type and one n type semiconductor. A semiconductor diodes currentvoltage characteristic can be tailored by. Bring them together and join them to make one piece of semiconductor which is doped differently either side of the junction. If the depletion layer region has a distance d, it therefore must therefore penetrate into the silicon by a distance of dp for the positive side, and a distance of dn for the negative side giving a relationship between the two of. It changes into heat and the energy of light if the hall knocks against the electron on the bonded surface.
It is used for many forms of rectification for current levels both large and small, as well as high and low voltage levels, and this semiconductor device finds many uses in all manner of electronic circuit designs. Working of pn junction diode 1bh62 in forward bias. When a ptype semiconductor is suitably joined to ntype semiconductor, the contact surface in called pn junction. Unbiased pn junction diode unbiasing means, no voltage source is connected across the terminals of pn junction diode.
If the diode is forward biased, it allows the electric current flow. Both with pnp and npn transistor, flyback diode is must in reverse bias. Submit your answers and see how many you get right. Lightemitting diodes circuit, working principle and.
There is another type of breakdown named as avalanche breakdown generally seen in the normal diode which requires large amount of reverse voltage to break the junction. This simple animation video clearly explains the topics pn junction. The working principle of the light emitting diode is based on the quantum theory. The zener diode working principles and its various. By using adblocking software, youre depriving this site of revenue that is needed to keep it free and current. Pn junction diode in the reversebiased configuration is sensitive to light from a range between 400nm to nm, which includes visible light. How diode works, animation diode, animation pn junction, working of pn. By using adblocking software, youre depriving this site of revenue that is needed to keep it. To understand how a pn junction diode works, begin by imagining two separate bits of semiconductor, one ntype, the other ptype.
Understand exactly how a diode works, the characteristics of a diode, and forward and reverse bias. Here, we see that the direction of drift current is opposite to that of the diffusion current. It means when the reverse voltage is applied to the zener diode a strong electric field is developed at the junction which is enough to break the covalent bonds within the junction and causes large flow of current through. When diode is reverse biased, majority carriers are blocked and only a small current flows through the diode due to the minority charge carriers. Shockley diode working principle engineering tutorial. Vi characteristics of pn junction diode in 3biasing modes. A schottky diode is formed by joining a doped semiconductor region usually ntype with a metal such as gold, silver, or platinum. The voltage v barrier causes an opposing current flow, and the two flows form an equilibrium. The pn junction is the fundamental building block of the electronic age.