Nptel video lectures, iit video lectures online, nptel youtube lectures, free video lectures, nptel online. The pn junction is the root for semiconductor diodes. Semiconductor pn junction diodes physically, diodes are formed by the interface between two regions of oppositely doped semiconductor i. This causes electrons from nregion to get attracted to positive terminal of the battery and holes by the negative terminal. A pn junction is a boundary or interface between two types of semiconductor materials, ptype and ntype, inside a single crystal of semiconductor. It is one of the simplest semiconductor devices as. Chitralekha mahanta nptelhrd fourier transform, fourier series, and frequency spectrum duration. Pn junction diode the symbol of diode is shown in fig. 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, whereas the zener diode allows the current to flow both in the forward and the reversed direction. The load resistance r l is connected to these terminals through a pn junction diode d. A pn junction with open terminals excluding minority carriers f. The pn junction biasing the pn junction the diode trouble shooting.
As the applied voltage increases, current starts to flow across the junction. A pn junction diode is made by forming a ptype region of material directly next to a ntype region. The other differences between the pn junction and zener diode are explained below in the comparison chart. If positive potential is applied to the top terminal as shown in fig. The quasineutral pregion is from the edge of the depletion region, which we will call x p, to the edge of the diode, which we assume is an infinite distance away from x p. An abrupt silicon pn junction n a 10 16 cm3 and n d 4 x 10 16 cm3 is biased with v a 0. May 17, 2020 a pn junction is the simplest form of the semiconductor diode. The pn junction is a versatile element, which can be used as a. This allows electrical current to pass through the junction only in. Pnjunction diode and diode circuits 1 main properties of semiconductors 2 the pnjunction in equilibrium 3 the i v characteristics of the pnjunction 4 deviations from the ideal diode 5 analysis of the diode circuits 6 rectifier circuits. The other differences between the pnjunction and zener diode are shown in the comparison chart. As shown in the figure, pn junction diode is a 2 terminal polarity sensitive device. Pn junction underbiasing 14 boltzmanns approximation. The recombination at the junction allows battery current to flow through the pn junction diode.
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. Junction diodes questions and answers electronics post. Definition, symbol, and types of diodes electrical4u. The quasineutral nregion is from the edge of the depletion region, which we will call x n, to the edge of the diode, which we assume is an infinite distance away from x n.
The pn junction has the very useful property that electrons are only able to flow in one direction. Review, pn junctions, fermi levels, forward bias prof j. 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. Jan 29, 2019 pn junction diode is one of the fundamental elements in electronics. It has a particular voltage known as break down voltage, at which the diode break downs while reverse biased. The pn junction solidstate device theory electronics. Generation of electronhole pairs in the depletion region. The shaded regions below illustrate the increase in the characteristics of the space charge region due to an externally applied reverse bias, v d. 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. Now, if we join the two types of semiconductors ptype and ntype together then a new device is formed called as pn junction diode. Lecture 15 the pn junction diode i iv characteristics november. At this point, a small increase in voltage increases the electric current rapidly. The boltzmann approximation is to say that the resulting current being small compared with the components of this current, we consider that we are still in quasi equilibrium and therefore that the currents equation is still valid by replacing v bi by v. Pnjunction diode characteristics ppt documentation.
When the diode is forwardbiased, it can be used in led lighting applications. Semiconductor, silicon, pn junction, forward bias, reverse bias, diode. A pn junction diode is a twoterminal electronics element, which can be classified as either. The diode conducts when forward bias is applied and it will introduce zero resistance in the circuit.
In the positive half cycle, during the time interval 0 to t2, diode d will be forward biased and conduct, i. Forward bias current flows reverse bias no current flow. At the point of the junction, which we call the metallurgical junction, is where n d n a 0. Zener diode is a pn junction diode specially designed to operate in the reverse biased mode. 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. Pn junction diode and characteristics of pn junction diode. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. Pn junction diode, characteristics and applications 2020. Lecture 16 the pn junction diode ii equivalent circuit model november 3, 2005 contents.
Pn junctions consist of two semiconductor regions of opposite type. Octavian florescu 2 the pn junction diode schematic diagram ptype ntype id. The terminal connected to player is called anode a and the terminal connected to nlayer is called cathode k fig. 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. We can then fill in the junction region of the band diagram as. A semiconductor diode is a two terminal electronic component with a pn junction. Why does the pn junction diode exhibit current rec tification. This lecture uncovers the basic science of semiconductor devices and solar cells, including pn junction and photovoltaic effects. Lecture 16 the pn junction diode ii mit opencourseware. The horizontal line in the below figure represents the amount of voltage applied across the pn junction diode whereas the vertical line represents the amount of current flows in the pn junction diode. 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. P type and n type semiconductors, takenseparately are of very limited use.
Apr 05, 2019 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. 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. If you continue browsing the site, you agree to the use of cookies on this website. Sep 10, 2016 pn junction and zener diode 12 class project slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity. The pn junction is the fundamental building block of the electronic age. Sep 21, 2014 electronic materials, devices, and fabrication by prof s. If positive terminal of dc source is connected to cathode and negative terminal is connected to anode, the diode is called reverse biased as shown in fig. Zero bias no external voltage potential is applied to the pn junction diode. The valence band and conduction band in ntype material are slightly lower than that of ptype material. 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. Such junctions show a pronounced rectifying behavior.
It is the most essential and the basic building block of the electronic device. This presentation is a very informative piece on pn junction diode an important part of electronics education. Since a junction forms between a p type and n type material it is called as pn junction. Semiconductor physics semiconductors and diodessemiconductors. The barrier potential of the diode is the voltage at which appreciable. Smith department of eecs university of california, berkeley eecs 105 spring 2004, lecture 19 prof. 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. Vi characteristics of pn junction diode electronics post. The anode which is the positive terminal of a diode is represented with a and the cathode. Parasuraman,department of metallurgy and material science,iit madras.
How a pn junction formed in a diode engineering tutorial. Electronic materials, devices, and fabrication by prof s. 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. On the other hand, if the diode is reverse biased, it blocks the. Working of pn junction diode with biasing, characteristics. A pn junction is formed by diffusing a ptype material to an ntype wafer and there are several other ways as well, see your text.
It is one of the simplest semiconductor devices as it allows current to flow in only one direction. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. Diodes what are diodes pn junction forward bias reverse. The pnjunction is the root for semiconductor diodes. They are also called pn diodes in analogy with vacuum diodes. Also, it explains the phenomenon of shockleyqueisser limit. Iv characteristics pn junction diode reverse biasing a pn junction when the polarity of the battery is reversed, the cathode is connected to positive end of the battery and anode to negative.
Ee105 fall 2014 microelectronic devices and circuits. Why does the junction current in forward bias increase. Introduction to semiconductors and the pn junction 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. This is the basic construction of the pn junction diode. 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.
Semiconductor pnjunction diodes physically, diodes are formed by the interface between two regions of oppositely doped semiconductor i. The pn junction diode is the basic semiconductor diode format. In the case of normal diodes the diode damages at the break down voltage. Ive tried to make this explanation as simple as possible so that no conceptual doubts arise. Pn junction diode 10 depletion width increases with reverse bias voltage. If the diode is forward biased, it allows the electric current flow. The forward voltage at which the silicon diode starts allowing large electric current is called cutin. Pn junction tutorial introduction to pn junction diodes.
Introduction to semiconductors and the pn junction diode robert clancy 04329741 april 10, 2006 abstract in this experiment the iv characteristicof the pn junction diode is determined andthe applicationofthe diodeasarecti. 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. Pn junction diode baising and its vi characteristics. Draw the energy level diagram of a pn junction and explain how a junction barrier is developed across an unbiased junction. 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. The potential at terminal x with respect to y will vary as a sine function with time. Najmabadi, ece65, winter 2012 high concentration of h on the p side holes diffuse towards the junction high concentration of. The word diode can be explained as di means two and ode is obtained from electrode. Diodes what are diodes pn junction forward bias reverse bias zener diodes. After having known about various components, let us focus on another important component in the field of electronics, known as a diode. Silicon a single silicon atom consists of fourteen negatively. Before going to the working, i would like to explain. From the above, it follows that zero power dissipation occurs in an ideal diode. Energy required for charge carriers to cross the depletion region decreases exponentially.
Simplified physical structure construction on a cmos chip. Specialpurpose diodes 129 actually contain two pn junctions that are connected in reverseparallel i. Consider an ideal pn junction diode with crosssection dimension of 10 um x. Vi characteristics of pn junction diode in 3biasing modes.
When the external voltage applied on the silicon diode reaches 0. The doping profile is our starting point to analyze pn junction electrostatics, since it combines the information given for n d and n a. The diode does not conduct when reverse bias is applied and. Pn junction diode 9 reverse bias external reverse bias adds to the builtin potential of the pn junction. The vi characteristics or voltagecurrent characteristics of the pn junction diode is shown in the below figure. It is acting as normal diode while forward biasing. Lecture 15 the pn junction diode i mit opencourseware.
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