Pn junction diode multiple choice questions answers. Light emitting diode, led circuit symbol led technology. In a schottky diode, a semiconductormetal junction is formed between a semiconductor and a. The n side will have large number of electrons and very few holes due to thermal excitation whereas the p side will have high concentration of holes and very few electrons. A diodes working principle depends on the interaction of ntype and ptype semico nductors.
In the same way if the nside is connected to the positive terminal of the supply and the pside to the negative terminal of the supply, the diode is said to be reversed biased. Gaas pn junctions from principles of electronic materials and devices, second edition, s. Free light emitting diodes books download ebooks online. Pn junction theory for semiconductor diodes basic electronics. The zener diode working principles and its various applications. Pn junction lab free to use on allows simulation and study of a pn junction diode with different doping and materials. Dec 11, 2017 diode seminar ppt and pdf report download. Lightemitting diodes circuit, working principle and.
With proper biasing, pn diode allows current to flow in single direction. 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. The basic difference between a forward bias and reverse bias is in the direction of. The pn junction diode is the basic semiconductor diode format.
The working principle of the light emitting diode is based on the quantum theory. These diodes have a very accurate and specific reverse breakdown voltage. P type and n type semiconductors, takenseparately are of very limited use. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner work ings of the pn junction. And adding leads and packages to the pn junction becomes a diode. They are also called pn diodes in analogy with vacuum diodes. In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity. Basic electronics nyu tandon school of engineering. This results in an empty zone around the pn junction that is free of charge carries creating a depletion region. There are two types of mechanism by which breakdown can occur at reverse pn junction that are avalanche and zener breakdown. 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.
The figure below shows the symbolic representation of a photodiode. Unbiased pn junction, forward biased pn junction and reversed biased pn junction. Most of the times a resistance has to be connected in series with it to limit the electric current flowing through the diode. Free electrons appear at room temperature due to breaking of the covalent bonds. What happens when we join ptype and ntype semiconductors. A pn junction diode is formed by doping one side of a piece of silicon with a ptype dopant boran and the other side with a ntype dopant phosphorus. 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 article provides a more detailed explanation of pn diode behavior than that found in the articles pn junction or diode a pn diode is a type of semiconductor diode based upon the pn junction. Current flow through a reverse biased pn junction diode. In a ptype semiconductor, the number p p of holes is much larger than the number of electrons n p p p n p. 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.
Diode operation no current flows because the holes and electrons are moving in the wrong direction. Zener diode working, characteristics and application as. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. Pnpn diode or shockley diode latest free electronics. When light emitting diode led is forward biased, the free electrons from nside and the holes from pside are pushed towards the junction.
Lecture 15 the pn junction diode i mit opencourseware. A diode is also a tool that exclusively permits unidirectional flow of current if the diode is operated at a particular voltage level. Rather than a pn junction, there is a metaltosemiconductor junction, as shown in below figure. 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. How a pnjunction diode works university of st andrews. Pn junction diode construction working and uses electrical. Pn junctions are formed in various kinds of semiconductor devices by several techniques. Since no free charge carriers can rest in a position where there is a potential barrier, the regions on either sides of the junction now become completely depleted of any more free carriers in comparison to the n and p type materials further away from the junction. 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. The principle of operation will be explained using a gedanken experiment, an. The schottky diode is an electronic component which is used to radio frequency rf functions like a mixer or a detector diode. 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.
Animation how a p n junction semiconductor works forward. Depletion layer opposes only the the majority carrier not minority carrier. The pn junction is a versatile element, which can be used as a. Varactor diode definition, symbol, construction and.
By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. Check our section of free ebooks and guides on light emitting diodes now. Are specifically designed to operate under reverse breakdown conditions. Pn junction diode and diode characteristics basic electronics. 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. The crystalline diode is a pn junction formed by a ptype semiconductor and an ntype semiconductor. Since no free charge carriers can rest in a position where there is a potential barrier, the regions on either sides of the junction now become completely depleted of. This understanding will lay a better foundation for exploring further into different aspects of semiconductor electronics. The construction of led is similar to the normal pn junction diode except that gallium, phosphorus and arsenic materials are used for construction instead of silicon or germanium materials. However, unlike a resistor, a diode does not behave linearly with respect to the applied voltage as the diode has an exponential currentvoltage iv relationship and therefore we can not described its operation by simply using an equation such as. How it doesnt work when a diode is connected to a battery as shown, holes in the nside are forced to the left while electrons in the pside are forced to the right. Semiconductor theory the active portion of a zener diode is a semiconductor pn junction.
Pn junction diode, characteristics and applications 2020. Pn junction diode and characteristics of pn junction diode. It acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator zener diode. The working principle of a pn junction diode can be broadly understood under three categories. 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. When the diode is forwardbiased, it can be used in led lighting applications. Pn junctions consist of two semiconductor regions of opposite type. Pn junction diode in the reversebiased configuration is sensitive to light from a range between 400nm to nm, which includes visible light. Questions you should be able to answer by the end of todays lecture. Fundamentally, all electrons and holes are swept out of the free space charge region by the electric field. The diode the diode is a two terminal semiconductor device that allows current to flow in only one direction. The depletion region is a region in a pn junction diode where mobile charge carriers free electrons and holes. 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 practical circuit arrangement for a pn junction diode is as shown in the following figure.
A free powerpoint ppt presentation displayed as a flash slide show on id. This lower voltage drop provides better system efficiency and higher switching speed. The junction of n and p semiconductors is free of charge carriers. In this article, we are going to explain zener diode and its applications in detail. In our previous articles, we explain in detail about diodes, pn junction diode, semiconductors etc. The photon energy is equal to the energy gap between these two energy levels. To understand how a pn junction diode works, begin by imagining two separate bits of semiconductor, one ntype, the other ptype. Diode working principle and types of diode electrical. Hbd854 zener theory and design considerations handbook. A zener diode is similar to conventional pn junction diode except that it is properly doped to achieve sharp breakdown voltage.
Oct 09, 2018 the circuit symbol of pn junction diode is shown below. Zener breakdown is caused at very low voltages when compared to the avalanche breakdown. Before going to varactor diode, lets first take a look at the capacitor. Light emitting diode led working, construction and symbol. The pn junction is an interface between a ptype and an ntype region and is used to construct diodes and transistors. It functions like a normal diode without any trigger inputs, in reverse biased condition, no current flows through it and in forward biased condition current flows through it. If this reverse biased voltage across the diode is increased continually, the depletion layer becomes more and more wider. 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. Jan 16, 2018 pn junction diode is a device made of two semiconductor material joined together with the required amount of impurity. Theoretical background semiconductor diode theory is at the very. Semiconductor pn junction diode working pn diode vi. One terminal of pn junction diode is anode and other is cathode.
A simple explanation of the working principle of a diode. Ppt pn junction diode powerpoint presentation free to. Working of pn junction diode with biasing, characteristics. Zener diodes are normal pn junction diodes operating in a reverse biased condition. Understanding about the pn junction diode theory and working. 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 is the most fundamental device element that forms the basis of many electronic devices such as pn diodes, optoelectronic devices like lightemitting diode and photodetector, field. In its basic form a semiconductor diode is formed by making pn junction which is. Such junctions show a pronounced rectifying behavior. However, unlike a resistor, a diode does not behave linearly with respect to the applied voltage as the diode has an exponential currentvoltage iv relationship and therefore we can not described its operation by simply using an equation such as ohms law.
Thus a reverse biased pn junction does not conduct current. Chapter 1 semiconductor pn junction theory and applications. Jul 29, 2016 a simple explanation of the working principle of a diode. If we join a piece of p type material to a pieceof n type material such that the crystalstructure remains continuous at the boundary, a pn junction is formed 2. Schottky diode working principle instrumentation tools. 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. Note to those familiar with a diode turn on voltage. Jan 29, 2019 pn junction diode is one of the fundamental elements in electronics. It is a pn junction diode, which emits light when activated. The shockley diode or pnpn diode is a four layer pnpn, two terminals namely anode and cathode semiconductor switching device. Depletion region created across the pn junction by the initial movement of majority carrier across the junction. This article covers the zener diode definition, working principle, characteristics, and applications. Discoveries and early devices, blue led, white leds and the illumination breakthrough, working principle, technology, efficiency and. 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.
Varactor diode is a pn junction diode whose capacitance is varied by varying the reverse voltage. Light emitting diode led working, construction and. In this article, i will explain the working principle of pn junction semiconductor diode. The led is a specialised form of pn junction that uses a compound junction. A schottky diode is formed by joining a doped semiconductor region usually ntype with a metal such as gold, silver, or platinum. The main principle of a diode is to use the unidirectional conductivity of the pn junction. In silicon, the bonding energy of the covalent bond is 1. A pn junction diode is a twoterminal electronics element, which can be classified as either. 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. Schottky diode working principle engineering tutorial. When diode is reverse biased, majority carriers are blocked and only a small current flows through the diode due to the minority charge carriers.
During the operation, when the diode is in forward biased condition, at some particular voltage, the potential barrier gets eliminated. Apr 23, 2018 semiconductor pn junction diode is the simplest semiconductor device. Although the basic pn junction had been in use for many years, it was not until 1962 that the led was developed and its action started to be understood. Silicon a single silicon atom consists of fourteen negatively. 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. An ammeter is connected in series and voltmeter in parallel, while the supply is controlled through a variable resistor. Understand exactly how a diode works, the characteristics of a diode, and forward and reverse bias. If a suitable positive voltage forward bias is applied between the two ends of the pn junction, it can supply free electrons and holes with the extra energy they.
Schottky diode definition, symbol, vi characteristics. Working principle of diode what happens inside the pn junction diode. Basic diode electronics introduction to diodes the pn junction the pn junction is a homojunction between a ptype and an ntype semiconductor. The pn junction diode is the typical diode that has been used in the previous circuits. Bring them together and join them to make one piece of semiconductor which is doped differently either side of the junction. Definition, symbol, and types of diodes electrical4u. Pn junction matse 081 materials in todays world working principle of zener diode when a pn junction diode is reverse biased, the depletion layer becomes wider. It works on the principle of photoelectric effect the operating principle of the photodiode is such that when the junction of this twoterminal semiconductor device is illuminated then the.
The zener diode is a special type of diode that is designed to work in reverse bias and in the socalled zener region of the diode characteristic curve. How a pn junction formed in a diode 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. The diode conducts current in only one direction, and it is made by joining a ptype semiconducting layer to an ntype semiconducting layer semiconductor diodes have multiple uses. Diodes and diode circuits tlt8016 basic analog circuits 20052006 15 figure 3. If the diode is forward biased, it allows the electric current flow.
The terms depletion itself means that there is a depletion of free charges in the region i. When a bond is supplied with this amount of energy or more an elec tron can break free. 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. Pn junction diode baising and its vi characteristics elprocus. When free electrons reach the junction or depletion region, some of the free electrons recombine with the holes in the positive ions. If an appropriate positive voltage forward bias is applied between the 2 ends of the pn junction, it will provide free electrons and holes with the additional energy they need to cross the junction because the breadth of the depletion layer round the pn junction is shriveled. A tunnel diode is a heavily doped pn junction diode in which the. Contd notes and anderson2 sections part 2 preface and sections 5. The pn junction is the fundamental building block of the electronic age. The circuit symbol of pn junction diode is shown below. Diodes exclusively block current in the reverse direction whereas the reverse voltage is within a restricted vary and if not reverse barrier breaks and conjointly the. Working principle of pn junction diode polytechnic hub. In normal pn junction diodes, silicon is most widely used because it is less sensitive to the temperature.
This article discusses about pn junction diode, diode theory of zero bias, forward bias, reverse bias with vi characteristics and its applications. May 19, 2014 how diode works, animation diode, animation pn junction, working of pn junction, how does a pn junction semiconductor works, what is avalanche breakdown, what is drift current, how drift current. As you know that a diode operates both in forward bias and reverse bias so explaining the both in detail with necessary vi characteristics curves. 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. Schematic symbol for a pn junction diode p n representative structure for a pn junction diode zener diodes. These materials are ntype, having electrons are majority carrier and ptype material, having holes are majority carrier. It comes useful for functions having power because of possessing low forward voltage drop that would result in power loss at the least levels in comparison to the general pn junction diodes. Laser diode working principle instrumentation tools. How a pn junction formed in a diode instrumentation tools.
This means that greater the intensity of light falling on the pn junction of photo diode, the greater will be the reverse current. This area around the pn junction is now called the depletion layer. 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. It is constructed of a p and an n junction connected together. The negative terminal of the battery is connected to the anode of a diode and positive terminal of battery is connected to cathode. Diodes exclusively block current in the reverse direction whereas the reverse voltage is within a restricted vary and if not reverse barrier breaks and conjointly the voltage at that this breakdown happens is termed. Due to this a process called diffusion takes place. An ntype semiconductor has plenty of free electrons and a very few numbers of holes. Pn junction semiconductor diode free online tutorials. Pn junction diode baising and its vi characteristics. Semiconductor pn junction diode is the simplest semiconductor device.
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