Similarly, holes in the ptype material will tend to diffuse into the ntype material. A pn junction is the simplest form of the semiconductor diode. Najmabadi, ece65, winter 2012 high concentration of h on the p side holes diffuse towards the junction high concentration of e on the n side electrons diffuse towards the junction n side is positively charged because it has lost electrons. Diodes have a forward direction and a reverse direction. Pn junction diode is a device made of two semiconductor material joined together with the required amount of impurity. These are the easiest and basic diodes available in and use pn junction characteristics like depletion layer, diffusion and drift current. Pn junction diode explained forward bias and reverse bias. Working of pn junction diode if an external potential is applied to the terminals of pn junction, it will alter the potential between the p and nregions. A diode is a twoterminal device formed by placing a layer of ptype semiconductor next to n type semiconductor. Smith department of eecs university of california, berkeley eecs 105 spring 2004, lecture 19 prof.
Lecture 16 the pn junction diode ii equivalent circuit model november 3, 2005 contents. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. Diode pn junction when p and n type silicon are brought together during manufacture, a junction is created where the p type and n type materials meet, and holes close to the junction in the p type silicon are attracted into negatively charged n type material at the other side of the junction. Power diodes have higher leakage current values as their pn junction has a larger crosssectional area. Semiconductor, silicon, pn junction, forward bias, reverse bias, diode. In pn junction electrons from ntype material tend to diffuse into the ptype material. When the ntype semiconductor and ptype semiconductor materials are first joined together a very large density gradient exists between both sides of the pn junction. Understand the behaviour of a diode under forward and reverse bias and be able to plot the iv characteristic of an ideal diode 3. The working principle of a pn junction diode can be broadly understood under three categories. The credit of discovery of the pn junction goes to american physicist russel ohi of bell. The pnjunction is the root for semiconductor diodes. Image source forward biasing a pn junction diode is very simple.
Definition, symbol, and types of diodes electrical4u. The forward voltage drop is an intrinsic property of the semiconductor material used to make the pn junction and is related to the band gap. A pn junction is a boundary or interface between two types of semiconductor materials, ptype. Zero bias no external voltage potential is applied to the pn junction diode. 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. Doping with acceptor creates p type semiconductor while doping with donors produces n type. Pdf diodes are electronic components functions as a oneway valve it.
A basic tutorial on characteristics and working of pn junction diode. A semiconductor pn junction diode is a two terminal electronic device that allows current in only one direction. Boron or aluminium from one end to form ptype region and with pentavalent impurity like. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner work ings of the pn junction. The pn junction biasing the pn junction the diode trouble shooting. The word diode can be explained as di means two and ode is obtained from electrode. Silicon a single silicon atom consists of fourteen negatively. If the pside anode is connected to the positive terminal of the supply and the nside cathode to the negative terminal of the supply, the diode is said to be forward biased. By watching this video, you will learn the following. With proper biasing, pn diode allows current to flow in single direction.
Working of pn junction diode with biasing, characteristics. To understand how a pnjunction diode works, begin by imagining two separate bits of semiconductor, one ntype, the other ptype. If a battery is connected to a diode, current will flow. Understand the physics of a pnjunction and how a junction diode is created 2. So, in this pn junction tutorial, we will discuss some of the basics of a pn junction, how a pn junction is formed, characteristics of pn junction and many other aspects. The increase in resistance of the pn junction results in the junction behaving as an insulator. The principle of operation will be explained using a gedanken experiment, an experiment, which is in principle possible but not necessarily executable in. Pn junction diodes as the name suggests are diodes made up by combining one p type and one n type semiconductor. Understanding about the pn junction diode theory and working. Pnjunction diode characteristics ppt documentation. The pn junction forms a semiconductor device called pn junction diode. Now, if we join the two types of semiconductors ptype and ntype together then a new device is formed called as pn junction diode.
Pn junction diode baising and its vi characteristics. From the above, it follows that zero power dissipation occurs in an ideal diode. We now consider a pn diode with an applied bias voltage, va. Pn junction theory for semiconductor diodes electronicstutorials. Working principle of pn junction diode polytechnic hub. It is used for many forms of rectification for current levels both large and small, as well as high and low voltage levels, and it finds many uses in all manner of electronic circuits. The pn junction has the very useful property that electrons are only able to flow in one direction. Forward bias current flows reverse bias no current flow.
The pn junction is the fundamental building block of the electronic age. It is one of the simplest semiconductor devices as it allows current to flow in only one direction. Vi characteristics of pn junction diode in 3biasing modes. This pn junction forms a most popular semiconductor device known as diode. These materials are ntype, having electrons are majority carrier and ptype material, having holes are majority carrier. 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. This video explains complete process of diode working i.
The diagram shows the basic complete characteristic curves of the two types of diodes. A tunnel diode is a heavily doped pn junction diode in which the electric. Conventional current flows from positive to negative and is opposite to the direction that electron current flows. The diode is firmed by doping a semiconductor like silicon or germanium with trivalent impurity e. A pnjunction 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. 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. The name diode is derived from diode which means a device that has two electrodes. Applying an external dc voltage to the diode is called as biasing. The maximum blocking voltage of the germanium diode is lower. Abrupt depletion layer approximation let apply bias and calculate current through the pn junction currents in pn junction from sze, 1981. A pn junction diode is made by forming a ptype region of material directly next to a ntype region. Investigation of a barrier layer by the thermoprobe method pdf. Working principle of pn junction semiconductor diode. Semiconductor pnjunction diodes physically, diodes are formed by the interface between two regions of oppositely doped semiconductor i.
This potential difference can alter the flow of majority carriers, so that the pn junction can be used as an opportunity for the diffusion of electrons and holes. Draw the vi characteristics of pn junction diode and explain the operation of diodes as with other semiconductor devices is often described by a special graph called a characteristic curve. Derivation steps see extra file on web site for explanations. A pn junction with open terminals excluding minority carriers f. This allows electrical current to pass through the junction only. 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 is all about the pn junction diodes theory, working principle and its applications. And the working of this pn junction diode under forward and reverse bias has been explained. Pn junction is also a fundamental building block of many other semiconductor electronic devices such as transistors, solar cells, light emitting diodes, and integrated circuits. A pn junction is a boundary or interface between two types of semiconductor materials, ptype and ntype, inside a single crystal of semiconductor.
Although it is not discussed majorly outside the concept of pn junction diode and sometimes the transistor, a pn junction is an essential topic in semiconductor electronics. A pn junction diode allows electric charges to flow in one direction, but not in the opposite direction. Review, pn junctions, fermi levels, forward bias prof j. To make use of this pn junction diode we have to apply an external dc voltage to it. No generationrecombination in the depletion layer 6. A pnjunction is formed when an ntype material is fused together with a ptype material creating a semiconductor diode. Bring them together and join them to make one piece of semiconductor which is doped differently either side of the junction.
This is the basic construction of the pn junction diode. It is the most essential and the basic building block of the electronic device. Objective questions on pn junction diode electrical. Diode working principle and types of diode electrical. 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. The pn junction diode is the basic semiconductor diode format. An attractive animation is presented in this video with complete voice description. The result is that some of the free electrons from the donor impurity atoms begi. When the diode is in forward conduction, the voltage drop across the diode is constant. We believe that the information given in this article is helpful to you for a. The p positive side contains an excess of holes, while the n negative side contains an excess of electrons in the outer shells of the electrically neutral atoms there. Experimental methods py2108 2 1 learning objectives the objectives of this practical section are to 1. It is used in the construction of transistors, fet, gates and many other types of integrated circuits. Since a junction forms between a p type and n type material it is called as pn junction.
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