Working of pn junction diode with biasing, characteristics. Understanding about the pn junction diode theory and working. Image source forward biasing a pn junction diode is very simple. From the above, it follows that zero power dissipation occurs in an ideal diode. What happens when we join ptype and ntype semiconductors. 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 zener diode working principles and its various applications. For a silicon diode this voltage is approximately 0. The pn junction is the fundamental building block of the electronic age. This article discusses about pn junction diode, diode theory of zero bias, forward bias, reverse bias with vi characteristics and its applications. Zener diode working, characteristics and application as. The junction formed here is because of its terminals are the emitter and the base as well as the collector and the base. Before going to the working, i would like to explain. Semiconductor pn junction diodes physically, diodes are formed by the interface between two regions of oppositely doped semiconductor i.
Now, if we join the two types of semiconductors ptype and ntype together then a new device is formed called as pn junction diode. The other differences between the pn junction and zener diode are explained below in the comparison chart. Parametric solution of diode circuits is desirable. A pnjunction diode is formed by joining together ntype and ptype silicon. The pn junction has the very useful property that electrons are only able to flow in one direction. 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 transistors bjts there are two types of bjts, the npn and pnp the two junctions are termed the baseemitter junction and the basecollector junction in order for the transistor to operate properly, the two junctions must have the correct dc bias voltages the baseemitter be junction is forward biased. 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. Pn junction theory for semiconductor diodes electronicstutorials. How diode works, animation diode, animation pn junction, working of pn junction, how does a pn junction semiconductor works, what is avalanche breakdown, what is drift.
As a result it is almost impossible for any electrons or holes to cross the depletion zone and the diode current produced is virtually zero. When forward biased, a small voltage is required to get the diode current flowing. As it is in forwarding mode the majority carriers here are the holes these get inserted into the base region. The pn junction diode is the basic semiconductor diode format. An ntype semiconductor has plenty of free electrons.
Working of a pn junction current iv characteristic of reverse bias a pn junction diode. Semiconductor principles were unknown to the developers of these early. The diode the diode is a two terminal semiconductor device that allows current to flow in only one direction. A pn diode is a type of semiconductor diode based upon the pn junction. Understand the physics of a pnjunction and how a junction diode is created 2. In our previous articles, we explain in detail about diodes, pn junction diode, semiconductors etc. Questions you should be able to answer by the end of todays lecture. In this article, we are going to explain zener diode and its applications in detail. And the working of this pn junction diode under forward and reverse bias has been explained. Ee lecture notes university of california, berkeley. Investigation of a barrier layer by the thermoprobe method pdf. It is one of the simplest semiconductor devices as.
When an external voltage is applied to a diode such that it cancels the potential barrier and permits the flow of current is called as forward bias. It is therefore a basic tool for rectification in the. Definition, symbol, and types of diodes electrical4u. A pn junction diode is made of a crystal of semiconductor, usually silicon. In this bipolar junction transistor, the voltage across the emitterbase junction that is in forwardbias is always less than the collectorbase junction reversedbias. A diodes oneway gate feature does not work all the time. Working of the zener diode is similar to a pn junction diode in forwarding biased condition, but the uniqueness lies in the fact that it can also conduct when it is connected in reverse bias above its thresholdbreakdown voltage. How a pnjunction diode works university of st andrews. A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. The function of the shockley diode is similar to a normal diode without any initiate ips. Reverse voltage above 25 v destroys the junction permanentaly. We can then fill in the junction region of the band diagram as.
There are two operating regions and three possible biasing conditions for the standard junction diode and these are. The bipolar junction transistors consist of two types of transistors. 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 term junction implies the boundary or region of transition between n type and p type semiconductor material. When the diode is forwardbiased, it can be used in led lighting applications.
If this reverse biased voltage across the diode is increased. Calculate the ideal diode current assuming that the ntype region is much smaller than the. It is one of the simplest semiconductor devices as it allows current to flow in only one direction. Where four layers are pnpn and two terminals are anode and cathode. Pnp transistor basics construction, working principle. You just need to take a battery whose values can be varied from o to v volts, connect. 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. A pnjunction is formed when an ntype material is fused together with a ptype material creating a semiconductor diode. A pn junction diode meant to operate in the break down region is called a zener diode.
By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner work ings of the pn junction. Lecture 15 the pn junction diode i iv characteristics november 1, 2005 contents. Pn junction diode baising and its vi characteristics. Lecture 15 the pn junction diode i mit opencourseware. This article provides a more detailed explanation of pn diode behavior than that found in the articles pn junction or diode a pn diode is a type of semiconductor diode based upon the.
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 tutorial introduction to pn junction diodes. Semiconductor pnjunction diodes physically, diodes are formed by the interface between two regions of oppositely doped semiconductor i. The width of the depletion region of the cb junction is higher than the be junction. The junction in between the terminals of the emitter and the base is biased in forwarding condition. The emitterbase diode is connected in the forwardbias, whereas the collectorbase diode is connected in the reversedbias. Pn junction diode explained forward bias and reverse bias. This fact is emphasized so strongly in many textbooks that students usually dont think to ask when they measure a diodes forward voltage drop and find it to be considerably different than 0. By exploring the electrical properties of silicon, it is possible to acquire an. Ive seen too many students gain the false impression that silicon pn junctions always drop 0.
Reverse bias of pn junction when the voltage is applied this way round it tends to pull the free electrons and holes apart, and increases the height of the energy barrier between the two sides of the diode. If this reverse biased voltage across the diode is increased continually, the depletion layer becomes more and more wider. A diodes working principle depends on the interaction of ntype and ptype semico nductors. Such junctions show a pronounced rectifying behavior. 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. 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. Zener diode is a special kind of diode which permits the flow of current in the forward direction as well as in reverse direction when the voltage is above a certain voltage known as breakdown or zener voltage. May 19, 2014 how diode works, animation diode, animation pn junction, working of pn junction, how does a pn junction semiconductor works, what is avalanche breakdown, what is drift current, how drift current. To understand how a pn junction diode works, begin by imagining two separate bits of semiconductor, one ntype, the other ptype. It is constructed of a p and an n junction connected together. 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. Transistor and diode studies static properties of this type of diode structure was made, and numerical computations are being completed. They are also called pn diodes in analogy with vacuum diodes.
A pn junction is a boundary or interface between two types of semiconductor materials, ptype. 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. Let us now try to know what happens if a diode is connected in forward biased and in reverse biased conditions. Where, i d current through the pn junction, in amps. It is used for many forms of rectification for current levels both large and small, as well as high and low voltage levels, and. Understand the behaviour of a diode under forward and reverse bias and be able to plot the iv characteristic of. This is the basic construction of the pn junction diode. It is a semiconductor device and it comes in two general types. In other words, we can say that the concentration of free electrons is high and that of holes is very low in an ntype semiconductor. This article provides a more detailed explanation of pn diode behavior than that found in the articles pn junction or diode. In a small silicon diode operating at its rated currents, the voltage drop is. Shockley diode circuit with working and characteristics. Understanding the pn junction university of new south wales.
Zener diodes are normal pn junction diodes operating in a reversebiased condition. Pn junctions worksheet discrete semiconductor devices. Use the inequality for that diode state range of validity to find the range of circuit variable which leads to that state. To understand how a pnjunction diode works, begin by imagining two separate bits of semiconductor, one ntype, the other ptype. Diode operation no current flows because the holes and electrons are moving in the wrong direction.
Ive tried to make this explanation as simple as possible so that no conceptual doubts arise. The application of a reverse voltage to the pn junction will cause a transient current to flow as both electrons and holes are pulled away from the junction. Working of the zener diode is similar to a pn junction diode in forwarding biased condition, but the. A diode is a twoterminal electronic component that conducts current primarily in one direction. The pn junction diode the nature of the pn junction is that it will conduct current in the forward direction but not in the 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. Here we will describe the system characteristics of the bjt. Bias is the application of a voltage across a pn junction. The pn junction is a versatile element, which can be used as a. The be junction is forward bias and the cb is a reverse bias junction. A pn junction is a boundary or interface between two types of semiconductor materials, ptype and ntype, inside a single crystal of semiconductor. Dec 27, 2017 its working principle is when the diode is reverse biased, small leakage currents pass through the diode, when the reverse voltage is further increased the leakage current also increases which are fast enough to break few covalent bonds within the junction these new charge carriers further breaks down the remaining covalent bonds causing huge. The diode conducts current in only one direction, and it is made by joining a ptype semiconducting layer to an ntype semiconducting. When a pn junction diode is reverse biased, the depletion layer becomes wider.
Pn junctions worksheet discrete semiconductor devices and. An abrupt silicon pn junction n a 10 16 cm3 and n d 4 x 10 16 cm3 is biased with v a 0. When the potential formed by the widened depletion layer equals the applied voltage, the current will cease except for the small thermal current. Pn junctions consist of two semiconductor regions of opposite type. The zener diode working principles and its various. Zener diode is a special kind of diode which permits the flow of current in the forward direction as well as in reverse direction when the voltage is above a certain voltage known as breakdown or.
A pn junction diode allows electric charges to flow in one direction, but not in. Due to this characteristic, the diode finds number of applications as given below. The conversion of alternating current into direct current is known as rectification. Bipolar junction transistors bjt general configuration and definitions the transistor is the main building block element of electronics. The increase in resistance of the pn junction results in the junction behaving as an insulator. Draw the vi characteristics of pn junction diode and explain the operation of. Bring them together and join them to make one piece of semiconductor which is doped differently either side of the junction. Reverse bias of pn junction when the voltage is applied this way round it tends to pull the free electrons and holes apart, and increases the height of the energy barrier between the two sides. The application of the shockley diode is a relaxation oscillator circuit that is shown above. Solve each circuit with its corresponding diode equation. An ntype semiconductor has plenty of free electrons and a very few numbers of holes.
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. 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. Before going to the working, i would like to explain how exactly the junction diode is made.
When revrese voltage is increased beyond a value,called breakdown voltage,the reverse current increases sharply and the diode shows almost zero resistance. I s pn junction saturation current, in amps typically 1 picoamp. Apr 07, 20 when revrese voltage is increased beyond a value,called breakdown voltage,the reverse current increases sharply and the diode shows almost zero resistance. A diode cannot conduct in reverse biased condition. A pn junction diode is made by forming a ptype region of material directly next to a ntype region. Animation how a p n junction semiconductor works forward. 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. 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. Silicon a single silicon atom consists of fourteen negatively. Jul 27, 2015 the shockley diode is a two terminal and four layer semiconductor switching diode. By watching this video, you will learn the following.