The junction of n and p semiconductors is free of charge carriers. A forward bias corresponds to applying a positive voltage to the anode the ptype region relative to the cathode the ntype region. A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded. Equilibrium conditions pn junction under zero bias. 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 shows zero resistance in the forward direction and infinite resistance in the reverse direction. Pn junction diode is one of the fundamental elements in electronics. The diode has two terminals called a cathode and an anode. Because of its electrical properties, silicon is called a semiconductor. Pn junction diode vi characteristics using multisim youtube. Like any diode, the pn junction diode has two connections or electrodes.
Forwarding bias characteristics of pn junction diode the circuit for the study of forwarding bias characteristics of pn junction diode is shown in fig a. We now consider a pn diode with an applied bias voltage, va. A pn junction diode is formed with a n type semiconductor and a p type semiconductor and the doping level is normal or moderatethat is the fermi of p type will lie close to the valence band and the fermi of n type will lie c. Pn junction diode, characteristics and applications 2020. This is the basic construction of the pn junction diode. P type and n type semiconductors, takenseparately are of very limited use. A key difference is that a pn diode contains two depletion regions of opposite type.
As shown in the figure, pn junction diode is a 2 terminal polarity sensitive device. Silicon a single silicon atom consists of fourteen negatively. Minor project report on pn junction, zener diode, led characteristics 1. Voltampere vi characteristics of a pn junction or semiconductor diode is the curve between voltage across the junction and the current through the circuit. This presentation is a very informative piece on pn junction diode an important part of electronics education. In this tutorial, we will learn about pn junction diodes and in particular the characteristics and working of pn junction diode. Pn junction underbiasing 14 boltzmanns approximation. A pn junction at equilibrium is characterized by a depletion region where there are no. It is indicated earlier that when a pn junction diode is forward biased a large forward current flows, which is mainly due to majority carriers. At the point of the junction, which we call the metallurgical junction, is where n d n a 0.
In this article, we will look at the characteristics of junction diodes and learn how to analyze circuits containing diodes that operate in the forward, reverse, and breakdown biases. However, if the voltage applied on the diode is increased continuously, the pn junction diode reaches to a state where junction breakdown occurs and reverse current increases rapidly. Minor project report on pn junction, zener diode, led. 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. Normally the voltage is taken along the xaxis and current along yaxis. 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.
Before using this diode, it is necessary to know a little about its characteristics and properties with forward bias and reverse bias. Effect of reverse bias on vi characteristics of pn junction diode when a reverse bias is applied across a pn junction diode, there is an extremely small reverse current ir through the pn junction due to minority carriers. Pn junction diode v i characteristics of pn junction diode. For a current to flow across the pn diode junction it must be forward biased. The same number of minority carriers are being swept. Working of pn junction diode with biasing, characteristics. The iv characteristics in forward bias for different semiconductors is shown. Pn junction tutorial introduction to pn junction diodes. Usually, voltage is taken along xaxis and current along yaxis. The diode conducts when forward bias is applied and it will introduce zero resistance in the circuit.
Voltage ampere or vi characteristics of a pn junction are the curve between voltage across the junction and the circuit current. The pn junction supports unidirectional current flow. Lecture 15 the pn junction diode i iv characteristics november. A pn junction is formed by joining ptype and ntype semiconductors together in very close contact. 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. Pnjunction diode characteristics forward bias external battery makes the anode more positive than the cathode current flows in the direction of the arrow in the symbol. 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. Hence, the reverse saturation current remains constant with the increase in voltage. The voltage between pend and nend is increased from zero in suitable equal steps and the corresponding currents are noted down. Since a junction forms between a p type and n type material it is called as pn junction. This pn diode applications are very useful for beginners. This page of application notes section covers pn junction diode applications.
Characteristics of junction diodes technical articles. The word diode can be explained as di means two and ode is obtained from electrode. 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. Pn junction diode baising and its vi characteristics. Pn junction diode characteristics explained in detail. Pn junction diode characteristics and biasing analyse a. 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. 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. What is the difference between pn junction diode and. These minority charge carriers are supplied from other side of the junction, where those carriers are majority in number. One electrode of the semiconductor device is termed the anode and the other is termed the cathode. Reverse bias external battery makes the cathode more positive than the anode a tiny current flows opposite to the arrow in the symbol. Processing and classification of pn junctions diodes. This understanding will lay a better foundation for exploring further into different aspects of semiconductor electronics.
Semiconductor pnjunction diodes physically, diodes are formed by the interface between two regions of oppositely doped semiconductor i. Note to those familiar with a diode turn on voltage. Pn junction diode and its characteristics in chapter 1 understanding the pn junction, we have seen how a pn junction is formed from a ptype and ntype semiconductor. Fig b shows the forward bias characteristic curve of. 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 doping profile is our starting point to analyze pn junction electrostatics, since it combines the information given for n d and n a. This is the voltage across the diode at which it starts conducting. Bias characteristics of pn junction diode self study point. Electronics tutorial about the pn junction diode and the vi characteristics of pn junction diode when used as a diode rectifier.
The vi characteristics or voltagecurrent characteristics of the pn junction diode is shown in the below figure. Now, if we join the two types of semiconductors ptype and ntype together then a new device is formed called as pn junction diode. This causes electrons from nregion to get attracted to positive terminal of the battery and holes by the negative terminal. The pn junction is the fundamental building block of the electronic age. The term junction refers to the boundary interface where the two regions of the semiconductor meet. Derivation of vi characteristics of pn junction diode. Pn junction diode and characteristics of pn junction diode. A pn junction diode is a basic semiconductor device that controls the flow of electric current in a circuit. 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. Simulation using multisim of pn junction diode characteristics. It increases towards the junction and becomes n and pn on p and n side respectively in steady state. Lecture 15 the pn junction diode i mit opencourseware.
Vi characteristics of pn junction diode in 3biasing modes. 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. A reverse bias corresponds to a negative voltage applied to the cathode. Pn junction diode applications pn diode applications. 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. The current i pp decreases towards the junction, at the junction enters the nside and becomes i pn which further decreases exponentially. In vi characteristics of pn junction diode is two operating regions and three possible biasing conditions for the standard junction diode and these are. 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. We have also learned about diffusion current, depletion region. 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 analysis is very similar to that of a metalsemiconductor junction. A perfect diode is a device that only allows current to flow through it in one direction, i. A junction diode features markedly different noise characteristics in such differ ent bias conditions and junction sizes. From the above, it follows that zero power dissipation occurs in an ideal diode.
It is the most essential and the basic building block of the electronic device. Diode is a twoterminal electronic component that conducts electric current in only one direction. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. The other differences between the pnjunction and zener diode are shown in the comparison. Vi characteristics of pn junction diode electronics post. Physical integrated structure p side intrinsic pn junction. It is also required to obtain the capacitancevoltage characteristics of the diode.
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