Turn on voltage based on the builtin potential of the pn junction. Image source forward biasing a pn junction diode is very simple. The pn junction is the fundamental building block of the electronic age. The most common type of semiconductor diode is the silicon diode. Why does the pn junction diode exhibit current rec. 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. 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. Consider the heavily doped pn junction shown to the left and then apply a reverse bias to the junction. Turn on voltage based on the builtin potential of the pn junction reverse bias breakdown voltage due to avalanche breakdown on the order of several volts. Type semiconductor pn junction energy diagrams of the pn junction and depletion region diode operation. The circuit schematic symbol of a diode is shown in figure 5. 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. If an external potential is applied to the terminals of pn junction, it will alter the potential between the p and nregions. Majority carriers that are injected to the opposite side.
The pn junction diode reverse bias is the condition that prevents current through the diode the negative terminal of the v bias source is connected to the p region, and the positive terminal is connected to the n region if the external reversebias voltage is increased to a large enough value, reverse breakdown occurs. The pn junction diode is the basic semiconductor diode format. Device physics i pn junctions depletion region neudeck p. The electrical characteristics of leds are the same as normal. The pn junction the pn junction is a homojunction between a ptype and an ntype semiconductor.
When the diode is forwardbiased, it can be used in led lighting applications. The semiconductor diode is a widely used electronics component found in many electronic circuit designs today. Pn junctions consist of two semiconductor regions of opposite type. Lecture 7 large and small signal modelling of pn junction. Energy required for charge carriers to cross the depletion region decreases exponentially. 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 load resistance r l is connected to these terminals through a pn junction diode d. The pn junction diode the negative terminal of the biasvoltage source pushes the conductionband electrons in the n region toward the pn junction, while the positive terminal pushes the holes in the p region toward the pn junction when it overcomes the barrier potential v b, the external voltage source provides the n region electrons with enough energy to penetrate the. 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.
Interesting to note that when you measure across the pn junction. Such junctions show a pronounced rectifying behavior. For more protection consider the following clipping circuit. 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. Wei es154 lecture 8 12 pn junction in reverse bias lets see how the pn junction looks with an external current, i less than is electrons leave the n side and holes leave the p side. The forward direction is shown in the schematic by the direction of the triangle. Pn junction diode lecture 2 outline about pn diode pn junction formation pn junction realization barrier height thermal equilibrium equilibrium depletion approximation abrupt junction pn junction bias. Circuit models of pn junction diodes small signal modeling of nonlinear circuit elements small signal models of pn junction diodes junction resistance and capacitances ece 315 spring 2006 farhan rana cornell university. P type and n type semiconductors, takenseparately are of very limited use. There are similarities and differences with pn junction diode. If the diode is forward biased, it allows the electric current flow. The pn junction biasing the pn junction the diode trouble shooting.
Pn junction diode baising and its vi characteristics. Zero bias no external voltage potential is applied to the pn junction diode. Diodes and diode circuits tlt8016 basic analog circuits 20052006 20 3. 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. Under forward bias, large positive current flows because the energy barrier for diffusion is reduced.
Contains a ptype and an ntype region in a closed boundary. When the diode is negative biased, no current can flow in the r, so vout 0. Recipe for solving diode circuits state of diode is unknown before solving the circuit 1. Notes for semiconductor devices psd by verified writer. The pn junction diode is the typical diode that has been used in the previous circuits. Understanding diodes discuss semiconductor materials. Gilbert ece 340 lecture 27 102912 zener breakdown last time we talked about zener breakdown the zener effect is the breakdown mechanism if the reverse bias required to force breakdown occurs at low voltages. Chitralekha mahanta, department of electronics and communication engineering,iit guwahati. Circuit symbol for the device is also shown with the \inward arrow depicting the ptype material side. The pn junction is a versatile element, which can be used as a rectifier, as an amplifier and as a voltageregulator and a switch. Instructors of courses using that text are permitted to use these lecture notes asis or adapt them for their use. Contd notes and anderson2 sections part 2 preface and sections 5. Pn junction diode lecture notes electronic device and circuit.
This lecture uncovers the basic science of semiconductor devices and solar cells, including pn junction and photovoltaic effects. It acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator zener diode. Basic diode electronics introduction to diodes the pn junction the pn junction is a homojunction between a ptype and an ntype semiconductor. But not exactly even if the external voltage or bias. Working of pn junction diode with biasing, characteristics. Diode schematic symbol and actual picture of a common 1n914 diode the black stripe in the picture is the cathode. 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.
Download pdf of note of pn junction diode by prabhat goud material offline reading, offline notes, free download in app, engineering class handwritten notes. 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. Pn junction diode and characteristics of pn junction diode. Wei es154 lecture 8 5 characteristics of junction diodes given a semiconductor pn junction we get a diode with the following characteristics. Also, note that this flatband diagram is not an equilibrium diagram since both electrons and holes can lower their energy by crossing the junction. Note to those familiar with a diode turn on voltage. Id decreases in equilibrium, there is a v r across the terminals greater than v 0 if i is, the. A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded. But not exactly even if the external voltage or bias is applied in the proper direction, no current flows until the depleted region becomes thin enough voltage needed to do this is called the diode drop if enough voltage is applied in the reverse bias direction. 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. Iv characteristics, practical ohmic contacts, smallsignal capacitance pn junction diodes lecture 10. Note of pn junction diode by prabhat goud material pdf download. Oct 07, 2008 lecture series on basic electronics by dr. Note that the dominant current component flowing across the metallurgical junction is that associated with minority.
Poissons equation, work function, ms energy band diagrams lecture 9. As the applied voltage increases, current starts to flow across the junction. Also, it explains the phenomenon of shockleyqueisser limit. The barrier potential of the diode is the voltage at which appreciable. Hence comparing the schematic symbol to the pn junction in figure 4, we see the anode is the ptype semiconductor and the cathode is the ntype semiconductor.
Lecture 6 biased pn junction diodes and current flow. The pn junction has the very useful property that electrons are only able to flow in one direction. Lecture notes in tffy 34 semiconductor technology september 12, 2000 page 2119 lecture 1 the band can be viewed as continuous. Pn junction diode is one of the fundamental elements in electronics.
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. Pn junction diode in the reversebiased configuration is sensitive to light from a range between 400nm to nm, which includes visible light. Lecture 15 the pn junction diode i iv characteristics november. Diodes in the first lecture, we discussed linear circuit components resistors, capacitors, and inductors. They are also called pn diodes in analogy with vacuum diodes. In the positive half cycle, during the time interval 0 to t2, diode d will be forward biased and conduct, i. State of diode is unknown before solving the circuit 1. Our pn junction behaves kind of like an ideal diode. This notes consists of introduction to bjt, itw working, different transistor configuration, biasing techniques, compensation techniques etc.
Led or a laser diode r ohms v9v va i v 1ir light emission under forward bias diode made from a direct bandgap semiconductor. From the above, it follows that zero power dissipation occurs in an ideal diode. The trapassisted current, avalanche breakdown, zener tunneling all could be calculated in a manner very similar to junction diode. Notes for semiconductor devices psd by verified writer lecture notes, notes, pdf free download, engineering notes, university notes, best pdf notes, semester, sem, year, for all, study material.
These devices may not be a simple pn type diode, but behave electrically identical to a pn junction diode. The pn junction when ptype and ntype semiconductors brought in contact with each other, we observe a drastically changed behavior and set of new properties, from the resulting device. Use the diode equation for that state to solve the circuit equations and find i d and v d 3. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. The more holes or free electrons there are, the more particles will diffuse across the junction. The potential at terminal x with respect to y will vary as a sine function with time. Write down all circuit equations and simplify as much as possible 2. Semiconductor pn junction diodes physically, diodes are formed by the interface between two regions of oppositely doped semiconductor i. The pn junction is also called as semiconductor diode. Ec is the lowest possible conduction band energy, while ev is the highest possible valence band energy. Semiconductor, silicon, pn junction, forward bias, reverse bias, diode. Diodes and diode circuits tlt8016 basic analog circuits 20052006 a. Lecture series on electronics for analog signal processing i by prof.
Although there are many different types of diode which use the same basic structure of an area of ptype material meeting an area of ntype material, the different types are optimised to provide different characteristics which can be used in a variety of ways in many electronic. Diodes and diode circuits tlt8016 basic analog circuits 20052006. It acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator zener diode, switching or tuner varactor diode. 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. Jul 31, 2017 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. Silicon a single silicon atom consists of fourteen negatively. Whites, ee 322 lecture 3 page 2 of 10 the diode has four characteristic regions fig. The pn junction is a versatile element, which can be used as a. A pn junction diode in thermal equilibrium you have already seen a pn junction diode in thermal equilibrium. Lecture 16 the pn junction diode ii mit opencourseware. Lecture 7 large and small signal modelling of pn junction diodes in this lecture you will learn. Diodes allow current to flow only in the forward direction. Niknejad pn junction capacitor under thermal equilibrium, the pn junction does not draw any much current but notice that a pn junction stores charge in the space charge region transition region since the device is storing charge, it s acting like a capacitor positive charge is stored in the nregion, and. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction.
In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity. Semiconductor pn junction diodes can be formed from materials other than. A k schematic symbol for a pn junction diode p n representative structure for a pn junction diode. Octavian florescu 2 the pn junction diode schematic diagram.
640 355 543 598 783 998 324 1072 1235 65 229 76 671 575 567 771 1056 161 319 1111 79 612 267 538 695 207 530 1274 1049 1296 22 829