Zener diode is a pn junction diode specially designed to operate in the reverse biased mode. The diode has two terminals called a cathode and an anode. Feb 20, 2018 theory of pn junction diode, diode current equation. Essentially it is the very high doping levels used in the tunnel diode its unique properties and characteristics. If a conductor is suppose to conduct current does that mean a semiconductor partially conducts current.
This post includes explanation of operation of zener diode and vi characteristics of zener diode. Once that happens, large current flows through the junction and the diode may get destroyed. The result is that some of the free electrons from the donor impurity atoms begi. A perfect diode is a device that only allows current to flow through it in one direction, i. Pn junction diode vi characteristics in forward and. Pn junction diode characteristics electronic circuits and. Connecting a pn junction to an external voltage source is biasing a pn junction. Zero bias no external voltage potential is applied to the pn junction diode.
Voltampere v i characteristics of a pn junction or semiconductor diode is the curve between voltage across the junction and the current through the circuit. Further increase in voltage does not increase this current. To study and verify the functionality of a pn junction diode in forward bias. J1 and j3 become reverse biased and the centre junction j2 becomes forward biased. Zero bias no external voltage is applied to the pn junction diode. Ideal diode and real diode a diode is said to be an ideal diode when it is forward biased and acts like a perfect conductor, with zero voltage across it. Electronics tutorial about the pn junction diode and the vi characteristics of pn junction diode when used as a diode rectifier. Zener diode is a reversebiased heavilydoped pn junction diode which operates in the breakdown 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.
This is the basic construction of the pn junction diode. It consists of a pn junction diode and when voltage is applied to the led, electrons and holes recombine in the pn junction and release energy in the form of light photons. This is a two terminal device consisting of a pn junction. In zener diode, electric current flows from both anode to cathode and cathode to anode. We hope that you have got a better understanding of this concept. Vi characteristics of pn junction diode electronics post. Tunnel diode theory shows that it does not act as a normal diode, but.
The tunnel diode was first introduced by leo esaki in 1958. A tunnel diode is a special type of pn junction diode that shows the negative resistance between two values of forward voltage ie, between peak point voltage and valley point voltage. It has a particular voltage known as break down voltage, at which the diode break downs while reverse biased. The primary difference between silicon and germanium diodes is the voltage needed for the diode to turn on or become forwardbiased. The vi characteristics of schottky barrier diode is steeper compared to vi characteristics of normal pn junction diode due to high concentration of current carriers. Pn junction diode baising and its vi characteristics elprocus. Pn junction diode shows zero resistance in the forward direction and infinite resistance in the reverse direction. The behaviour of a diode in a circuit is given by its iv characteristics.
Dec 16, 2017 a tunnel diode is a special type of pn junction diode that shows the negative resistance between two values of forward voltage ie, between peak point voltage and valley point voltage. 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. Pn junction diode baising and its vi characteristics. Mar 23, 2018 simulation using multisim of pn junction diode characteristics. V t1 where i do is reverse saturation current and will be very high in tunnel diode compared to pn junction diode due to high doping concentrations. Electrostatic analysis of a pn diode pn juntion diode. Iv characteristics pn junction diode theory a semiconductor pn junction diode is a two terminal electronic device that allows current in only one direction. Normally the voltage is taken along the xaxis and current along yaxis. Zener effect dominates at reverse voltages less than 5 volt whereas avalanche effect dominates above 5 v. The forward characteristic of a pn junction diode is non linear, i.
Working of pn junction diode with biasing, characteristics. The diode current in a tunnel diode is same as that for normal pn junction diode which is given as i diode i do exp v. The zener diode is a particular type of diode that solves this problem. In general, the cathode of a diode is marked by a solid line on the diode. Vi characteristics of pn junction diode in 3biasing modes. A key difference is that a pn diode contains two depletion regions of opposite type.
The vi characteristics of the ideal diode are shown in the figure below. The reverse breakdown of a pn junction may occur either due to zener effect or avalanche effect. The vi characteristics of the ideal diode are shown in. Apr 23, 2018 semiconductor pn junction diode is the simplest semiconductor device. Pn junction theory a pn junction is formed when an ntype material is fused together with a ptype material creating a semiconductor diode in the previous tutorial we saw how to make an ntype semiconductor material by doping a silicon atom with small amounts of antimony and also how to make a ptype semiconductor material by doping another. The contact surface between the layers of ptype and ntype semiconductor pieces plated together so as.
And based on the applied voltage, there are three possible biasing conditions for the pn junction diode, which are as follows. 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. The v i characteristics or voltagecurrent characteristics of the pn junction diode is shown in the below figure. In the case of normal diodes the diode damages at the break down voltage. Thyristor working, vi characteristics, types, applications. The contact surface between the layers of ptype and ntype semiconductor pieces plated together so as to form a pn junction is called the pn junction. 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. Pn junction diode is one of the fundamental elements in electronics. Pn junction diode vi characteristics using multisim youtube. However, we know from the previous tutorial that if we connect the external energy. Due to heavily doped, its depletion layer is very thin and is order of micrometer. Voltampere vi characteristics of a pn junction or semiconductor diode is the curve between voltage across the junction and the current through the circuit. Where i do is reverse saturation current and will be very high in tunnel diode compared to pn junction diode due to high doping concentrations, v is voltage applied across diode, v t is the voltage equivalent of temperature.
Tunnel diode basics, operation, vi characteristics. Derivation of vi characteristics of pn junction diode. Apr 05, 2019 in this tutorial, we will learn about pn junction diodes and in particular the characteristics and working of pn junction diode. P type and n type semiconductors, takenseparately are of very limited use. Its characteristics are completely different from the pn junction diode. We have seen how a diode is made with p and n semiconductors but. Forward and reverse characteristics of a pn junction diode. Before using this diode, it is necessary to know a little about its characteristics and properties with forward bias and reverse bias. A semiconductor diode is prepared by joining p and n sections of a semi conducting. A zener diode when forward biased behaves like an ordinary pn junction diode. Conduct the experiment for obtaining the forward bias vi characteristics of the given diode. A diode allow electric current to pass in forward direction and block current in reverse direction. A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded. The symbolic representation of the diode is as follows.
Basic electronics notes on vi characteristics of zener diode. For zener diodes, silicon is preferred to ge because of its high temperature and current capability. These diodes operate at a precise value of voltage called break down voltage. An ideal pn junction diode does not conduct in reverse biased condition. Therefore, this is all about pn junction diode in zero bias, forward bias and reverse bias conditions and vi characteristics of pn junction diode.
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. The forward bias characteristic of zener diode is same as the normal pn junction diode but in reverse bias it has different characteristic. It is one of the simplest semiconductor devices as it allows current to flow in only one direction. Tunnel diode working principle and characteristics ece. Theoretical background semiconductor diode theory is at the very center. Zener diode definition, vi characteristics, and breakdown. The basic diode symbol and static vi characteristics. Jan 21, 2019 vi characteristics of pn junction diode. We have also learned about diffusion current, depletion region.
The lead connected to the ptype material is called the anode and the lead connected to the ntype material is the cathode. A zener diode conducts excellently even in reverse biased condition. In this tutorial, we will learn about pn junction diodes and in particular the characteristics and working of pn junction diode. 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. The basics of tunnel diode theory enable an understanding of the oeprtion of the diode to be gained. A semiconductor device oracle magazine pdf primer doping and diodes. Voltage ampere or vi characteristics of a pn junction are the curve between voltage across the junction and the circuit current. If the anode is negative with respect to cathode, i.
Basics of led light emitting diode as mentioned in the introduction, an led is a semiconductor light source. This article discusses about pn junction diode, diode theory of zero bias, forward bias, reverse bias with vi characteristics and its applications. The diode is firmed by doping a semiconductor like silicon or germanium with. But for simplicity, both types are called zener diodes.
The breakdown voltage of a zener diode can be set by controlling the doping level. Pn junction theory a pnjunction is formed when an ntype material is fused together with a ptype material creating a semiconductor diode in the previous tutorial we saw how to make an ntype semiconductor material by doping a silicon atom with small amounts of antimony and also how to make a ptype semiconductor material by doping another. Derivation of vi characteristics of pn junction diode 4. Simulation using multisim of pn junction diode characteristics. I t is noted that at a certain reverse voltage, the reverse current reaches its maximum level. The analysis is very similar to that of a metalsemiconductor junction. It is also required to obtain the capacitancevoltage characteristics of the diode. We operate a zener diode in reverse biased conditions, and this diode does not get damaged even when the voltage across this exceeds the reverse breakdown voltage. Uniti diode current equation vi characteristics of pn junction. The primary difference between silicon and germanium diodes is the voltage needed for the diode to.
One terminal of pn junction diode is anode and other is cathode. Pn junction diode vi characteristics in forward and reverse bias. Forward and reverse characteristics of a pnjunction diode. Theory of pn junction diode, diode current equation. Plot the vi characteristics and calculate the resistance levels.
The potential developed across the junction due to the influence of the carriers is termed as diffusion voltage. Depletion layer opposes only the the majority carrier not minority carrier. Semiconductor pn junction diode working pn diode vi. Electrostatic analysis of a pn diode pnjuntiondiode. A pn junction diode is a twoterminal electronics element, which can be classified as either. A semiconductor diode is the most common type diode, which is a piece of semiconductor material with a pn junction connected to two terminals. The tunnel diode characteristics and operation depend upon some of the subtle differences between a normal pn junction and structure of the tunnel diode itself. Jan 02, 2019 once that happens, large current flows through the junction and the diode may get destroyed. Usually, voltage is taken along xaxis and current along yaxis. Similarly, when the diode is reversed biased, it acts as a perfect insulator with zero current through it. In the currentvoltage characteristics of junction diode, from the first quadrant in the figure current in the forward bias is incredibly low if the input voltage applied to the diode is lower than the threshold voltage vr.
A diode is a device that acts like a conductor since it allows current to pass in one direction known as forward biasing and it. 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. Diode theory what is a diode, or semiconductor for that matter. 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. The same number of minority carriers are being swept. Pn junction diode vi characteristics in reverse bias. If the positive terminal of the battery is connected to the ptype semiconductor and the negative terminal of the battery is connected to the ntype semiconductor, the diode is said to be in forward bias. 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. Schottky barrier diodeconstructionvi characteristics.
Pn junction diode characteristics and biasing analyse a. For the reverse characteristics of the given pn junction diode, a graph is plotted with reverse voltage along x axis and reverse current along y axis. Depletion region created across the pn junction by the initial movement of majority carrier across the junction. The vi characteristics or voltagecurrent characteristics of the pn junction diode is shown in the below figure. Donor impurities pentavalent are introduced into oneside and acceptor impurities into the other side of a single crystal of an intrinsic semiconductor. It is acting as normal diode while forward biasing. Both silicon and germanium can be combined with other elements called dopants to create solidstate electronic devices, such as diodes, transistors and photoelectric cells. 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. In a schottky barrier diode current conduction is through majority carriers which are electrons in. Pn junction diode theory and current conduction mechanisms. This understanding will lay a better foundation for exploring further into different aspects of semiconductor electronics. Basic electronics notes on vi characteristics of zener.
Pn junction underbiasing 14 boltzmanns approximation. Note to those familiar with a diode turn on voltage. Pn junction diode characteristics explained in detail. To study the forward and reverse bias characteristics of diode and zener diode. Compare the theoretical and practical values cutin voltage and resistances. Jan 29, 2019 pn junction diode is one of the fundamental elements in electronics. Pn junction diode and characteristics of pn junction diode. Semiconductor pn junction diode is the simplest semiconductor device. The symbol of zener diode is similar to the normal pn junction diode, but with bend edges on the vertical bar. The above are some of the basics of the pn junction diode and this article covers about the vi characteristics of the pn junction diode.
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