Junction diodes solidstate device theory electronics. 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. Chapter 1 semiconductor pn junction theory and applications. A pn junction with open terminals excluding minority carriers f. Theoretical background semiconductor diode theory is. We also explained how depletion region is created, what barrier potential is and what diffusion.
Pn junction diode is one of the fundamental elements in electronics. The symbolic representation of the diode is as follows. Simulator procedure as performed through the online labs select the characteristics of diode from the. Pn junction diode characteristics explained in detail. Pn junction diode and diode characteristics electronicstutorials. This same diode and its characteristics are shown in figure 1. 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. Vi characteristics of pn junction diode electronics post. Note to those familiar with a diode turn on voltage. 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. 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. Normally the voltage is taken along the xaxis and current along yaxis. Definition ptype semiconductor is suitably joined to ntype semiconductor,to conduct surface is called pn junction. This article discusses about pn junction diode, diode theory of zero bias, forward bias, reverse bias with vi characteristics and its applications.
The direction of arrow is the direction of conventional current flow under forward bias. A perfect diode is a device that only allows current to flow through it in one direction, i. A key difference is that a pn diode contains two depletion regions of opposite type. The light emitting diode or led as it is more commonly called, is basically just a specialised type of diode as they have very similar electrical characteristics to a 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. The pn junction has the very useful property that electrons are only able to flow in one direction.
The arrow indicates the flow of current through it when the diode is in forward biased mode, the dash or the block at the tip of the arrow indicates the blockage of current from the opposite direction. A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded. Pn junction diode baising and its vi characteristics elprocus. Zener diode is a pn junction diode specially designed to operate in the reverse biased mode. Diode current equation diode equation thermal voltage and ideality factor diode duration. An ideal pn junction diode does not conduct in reverse biased condition. Pn junction diode junction diode symbol and static iv characteristics. The behaviour of a diode in a circuit is given by its iv characteristics. In this article, we will focus on the iv characteristics of the junction diode, specifically the pn junction. P n junction theory and diodes part i gate problems. For the forward characteristics of the given pn junction diode, a graph is plotted with forward voltage along x axis and forward current along y axis.
It is also required to obtain the capacitancevoltage characteristics of the diode. The pn junction biasing the pn junction the diode trouble shooting. Iv characteristics pn junction diode theory a semiconductor pn junction diode is a two terminal electronic. The pn junction diode is the basic semiconductor diode format. In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity. A semiconductor diode is the most common type diode, which is a piece of semiconductor material with a pn junction connected to two terminals. Voltampere vi characteristics of a pn junction or semiconductor diode is the curve between voltage across the junction and the current through the circuit. The graph shows the reverse vi characteristics of the given pn junction diode. The vi characteristics of a diode can be forward or reverse.
The barrier increase reduces the majority carrier diffusion to a negligible level. This causes the holes to move toward the depletion region and the free electrons to move toward the depletion region. 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. Vi characteristics of pn junction diode in 3biasing modes. A very small current will made at the junction due to the movement of minority charge carriers across the junction. It has a particular voltage known as break down voltage, at which the diode break downs while reverse biased.
Donor impurities pentavalent are introduced into oneside and acceptor impurities. It generally shows the relation between bias voltage and current of a diode. In forward bias condition, current is constant until certain voltage is reached. As the name stands pn junction diode is made up of p type and n type semiconductor material. It is the most essential and the basic building block of the electronic device. If an external dc voltage is given to the circuit in which the semiconductor diode is a part of it, results in a qpoint or operating point on the pn junction diode characteristic curve that does not alter with time. Diode characteristics dynamic resistance, transition time. If a conventional pn junction diode is run into reverse breakdown it is most likely to be irreparably damaged. Pn junction diode characteristics and working elexfocus. The analysis is very similar to that of a metalsemiconductor junction.
A diode allow electric current to pass in forward direction and block current in reverse direction. 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. With proper biasing, pn diode allows current to flow in single direction. The crosssection in figure aboveb looks a bit more complex than a simple pn junction. Forward bias current flows reverse bias no current flow. These diodes operate at a precise value of voltage called break down voltage. Image source forward biasing a pn junction diode is very simple. Also in the next tutorial we will examine the signal diode static currentvoltage characteristics curve and parameters. Working of pn junction diode with biasing, characteristics. Pn junction diode and characteristics of pn junction diode. The depletion region shrinks allowing current to flow.
Junction coming to the equilibrium by balancing the fermi level ef ef the balance is achieved by electrons diffusing into a pside bringing an extra negative charge in there and by the holes diffusing into. Diodes which are designed with adequate power dissipation capabilities to operate the break down region may be employed as, experiment no 1. 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 diode characteristics vi forward and reverse pn junction diode is a semiconductor devices which conducts from only one side. Diode theory diode as a conductor when a voltage is applied current will flow. Pn junction diode is a device made of two semiconductor material joined together with the required amount of impurity. In the case of normal diodes the diode damages at the break down voltage. Questions you should be able to answer by the end of todays lecture.
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. 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. The result is that some of the free electrons from the donor impurity atoms begi. There are two operating regions and three possible biasing conditions for the standard junction diode and these are. This causes electrons from nregion to get attracted to positive terminal of the battery and holes by the negative terminal. The forward and reverse characteristics of the given pn junction diode is drawn. Theory of pn junction diode, diode current equation. This means that an led will pass current in its forward direction but block the flow of current in the reverse direction. Because of its electrical properties, silicon is called a semiconductor. The diode has two terminals called a cathode and an anode. Electrostatic analysis of a pn diode pnjuntiondiode. It is used majorly in rectifier and voltage regulator circuits. Now lets try applying an external voltage to the pn junction diode. The forward current shows a sudden increase at certain forward voltage, which is known as the knee voltage.
The pnjunction is the root for semiconductor diodes. Semiconductor, silicon, pn junction, forward bias, reverse bias, diode. 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. The pn junction is the fundamental building block of the electronic age. The vi characteristics or voltagecurrent characteristics of the pn junction diode is shown in the below figure. Diode characteristics physics astronomy project topics. In this physics video in hindi we explained the working of a pn junction diode for class 12. 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. Range of tunnel diode voltage for which the slope of the characteristics is ve is between v p and v v option c 11. Diode current equation vi characteristics of pn junction diodeapplication half wave rectifier and full wave rectifiers with and without filters derivation of ripple. 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. These materials are ntype, having electrons are majority carrier and ptype material, having holes are majority carrier. To plot voltampere characteristics of silicon pn junction diode. Silicon a single silicon atom consists of fourteen negatively.
Static resistance or dc resistance of a pn junction diode defines the diodes resistive nature when a dc source is connected to it. It is acting as normal diode while forward biasing. Compare the theoretical and practical values cutin voltage and resistances. Uniti diode current equation vi characteristics of pn junction. Plot a graph with reverse voltage along x axis and reverse current along y axis. This is a two terminal device consisting of a pn junction formed either in ge. A zener diode conducts excellently even in reverse biased condition. We have seen how a diode is made with p and n semiconductors but. To study and verify the functionality of a pn junction diode in forward.
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