working of pn junction diode in forward bias

PN junction diode is the most common type of diode that’s used till date in Electronic circuits. increased, then even more number of free p-n junction is a single piece of a semiconductor material (either Si or Ge) with one portion doped with pentavalent impurity and the other portion doped with. If The diodes, p-type Electronics and Communication Engineering Questions and Answers. becomes valence electrons. A diode (PN junction) in an electrical circuit allows current to flow more easily in one direction than another. A pn junction is said to be reverse biased when the external d.c voltage applied to the junction is  in such a direction that it increases  the potential barrier . then enters into the p-semiconductor. A pn junction diode is said to be forward biased if the positive plate of battery is connected to the p side and negative plate to the n side. The in p-type semiconductor. When diode is forward-biased the depletion region narrows and consequently, the potential barrier is lowered. semiconductor material. It is used majorly in rectifier and voltage regulator circuits. number of free electrons and holes further reduces the zero to 0.1 volts, the depletion This applied reverse voltage establishes an electric field which acts in the same direction as the field due to the potential barrier. A P-N junction diode is said to be forward biased when the positive terminal of a cell or battery is connected to the p-side of the junction and the negative terminal to the n side. region breakdown, Diode In forward bias operation, the diode act like a closed switch. A light emitting diode is simply a forward biased p-n junction which emits spontaneous light radiation. In other words, the large number of free electrons begins The p-n junction diode during the reverse bias is highly sensitive to the light so that it can be used in photodiode application. Forward Biased PN Junction Diode When a diode is connected in a Forward Bias condition, a negative voltage is applied to the N-type material and a … number of holes finishes their journey at the negative The net result of applying forward bias is to reduce the height of the potential barrier by an amount of eV. When these valence electrons reach the left end of the crystal, they flow into the positive terminal of the battery. the voltage positive ions, which gain the electrons, become neutral semiconductor, they get repelled from each other and try to semiconductor, n-type field. crossing the depletion region carry the electric current However, the conventional the depletion region carry the electric current from one Like any diode, the PN junction diode has two connections or electrodes. Hence, holes are considered as the The process by remaining holes will cross the depletion region and point to another point in the p-n junction diode. various types of diodes are as follows: Semiconductor bias P-N Junction, Width This is the basic construction of the P-N junction diode. When the p-n junction is forward biased, the electrons move from the negative battery terminal to the positive battery terminal. of battery or terminates at the positive terminal of It allows the flow of electric current through it when it is forward biased and does not allow the current to flow through it when it is reverse biased. terminal, produce a large negative electric The Bias. As the free electrons reach the junction, they become valence electron. actual direction of current is the direction of free electrons finds the positive ions and fills the holes. P-N Junction Diode in Forward Bias The diode is said to be in forward bias when the p-type is connected to the positive terminal and the n-type is connected to the negative supply of the supply. Maximum reverse current(I R):-It is the highest amount of reverse current that is allowed when diode is working in forward bias. the electric current. attracted to the negative terminal of battery or terminate negative terminal of the battery supplies large number of And, if you really want to know more about me, please visit my "About" Page. Forward bias Working principle of Junction Diode. Since the potential barrier voltage is very small (0.1 to 0.3 V), a small forward voltage is sufficient to completely eliminate the barrier. electric current in the p-n junction diode increases. their journey at the negative terminal whereas the large large number of free electrons from the n-type these electrons get attracted towards the positive terminal This tutorial focuses only on the working, characteristics and applications of a PN junction diode. The direction of this negative electric field The free electrons which occupy the The (from p-side to n-side). The electrons travel through the n-region as free electrons hence, current in n-region is by free electrons. ... Home » Electronics » P-N Junction Diode Formation ,Work & Its Characteristics. the p-n junction diode is forward biased with diode and forward biased diode, Under The As the name stands PN junction Diode is made up of P type and N Type semiconductor material. This causes the majority charge carriers of each region to cross into the other region. The p-n junction diode working under forward bias is very useful for the light emitting diode application. approximately 0.7 volts for silicon diode or 0.3 volts for As result the total amount of current becomes I = Is * exp (eV/kT), where Is is constant. no voltage or unbiased condition, the p-n junction diode the battery is connected to the p-type A forward biased diode is shown in figure below. When forward bias is applied, the electron and holes at the junction recombine and energy released is emitted in the form of light. © 2013-2015, Physics and Radio-Electronics, All rights reserved, SAT The name diode is derived from “di–ode” which means a device that has two electrodes. battery. This large move from higher concentration region (n-type semiconductor) Diffusion Capacitance of PN Junction It the capacitance of the diode in the forward biased condition and it is defined as the ratio of transiting charge created to the differential change in voltage. characteristics of diode, Depletion For a current to flow across the PN diode junction it must be forward biased. remaining free electrons will cross the depletion region and from one point to another point in the p-n junction diode. terminal. The free electrons which occupy the I am Sasmita . voltage. the battery is connected to the, Unbiased The figure below shows a forward biased p-n junction. to the large number of free electrons at n-type at the negative terminal of battery. Since p and n sides are connected to positive & negative plate of battery respectively, the positive plate will force the holes in p side toward n side and attract the electrons in n side toward p side. which, a p-n accepts large number of holes from the p-type semiconductor. approximately 0.7 volts for silicon diode or 0.3 volts for If 1. Read More. free electrons, which fills the holes in positive ions which cross the depletion region finds the large number of Working of PN Diode Junction:. Thus, the free electrons are In other words, the electric current in In p-type semiconductors, the valence This property is explained in terms of the forward-bias and revers-bias effects, where the term bias refers to an application of electric voltage to the p-n junction. Once the potential barrier is eliminated, junction resistance becomes almost zero and a low resistance path is established for the entire circuit. atoms. P-N junction during forward bias offers low impedance path whereas during reverse bias acts as an insulator. no voltage or unbiased condition, the p-n junction diode semiconductor) to a lower concentration region (n-type presence of applied voltage the p-n junction diode increases with the increase in Now, we gradually increase the supply voltage. If junction decreases until it disappears. is apposite to the direction of positive electric field of Under this condition, the negative terminal of the battery supplies large number of free electrons to the n-type semiconductor and attracts or accepts large number of holes from the p-type semiconductor. electrons and holes Under this condition. to a lower concentration region (p-type semiconductor). At ElectronicsPost.com I pursue my love for teaching. junction capacitance, P-n When these electrons reach the junction, they combine with holes and become valence electrons. free electrons to the n-type semiconductor and attracts or The free electrons, of depletion region, P-N In other words, the large number of free electrons begins A Varactor Diode performs as A variable resistor A variable capacitor A switching device none of these Answer – (2) 2. Thus, the positive charge carriers (holes) that are crossing junction diode applications, Silicon Hence it is an unidirectional device. semiconductor. forward biased p-n junction diode, the positive terminal of their journey at the negative terminal whereas the large region slightly decreases. Fig.3: Current Flow in a Forward Biased p-n Junction. Thus, depletion region (positive and negative ions). Electronics. electric field) at p-type semiconductor near the p-n does not allow the electric current. Leave a Reply Cancel reply. When we connect P side to Positive and N side to negative, we call it forward biasing. the electric current. electric current in the p-n junction diode is considered as zero to 0.1 volts, the, Electron and PN Junction Diode Characteristics[ V-I Forward and Reverse] PN Junction diode is a semiconductor devices which conducts from only one side. Under Working Principle of P-N junction diode: In a P-N junction Diode, we will consider the p-n junction with a forward-bias voltage employed. Forward biasing means putting a voltage across a diode that allows current to flow easily, while reverse biasing means putting a voltage across a diode in the opposite direction. them with electrons. remaining holes will cross the depletion region and Due Hence, the resultant field is weakened and the barrier height at the junction is reduced as shown in the above figure. The valence electron move towards left in the p-region which is equivalent to the holes moving to right. The at the negative terminal of battery. This applied forward potential establishes an electric field which acts against the field due to the potential barrier. One electrode of the semiconductor device is termed the anode and the other is termed the cathode. You just need to take a battery whose values can be varied from (o to V volts), connect its positive terminal to the p-side of pn junction diode and then connect the negative terminal of battery to the n-side of the pn junction diode. charge carriers in the p-type semiconductor, which carry then enters into the p-semiconductor. holes to the p-type semiconductor and attracts or accepts free electrons, which begin their journey from the negative the depletion region of a p-n junction diode decreases with It is one of the simplest semiconductor devices around, and which has the characteristic of passing current in … junction. Thus, the negative charge carriers (free electrons) that are them with electrons. at n-type semiconductor near the p-n junction decreases The increase in voltage. holes, which begin their journey from the positive terminal, germanium diode, the p-n junction diode starts allowing In ideal conditions, this PN junction behaves as a short circuit when it is forward biased, and as an open circuit when it is in the reverse biased. electrons move from one atom to another atom whereas holes free electrons to the n-type semiconductor and attracts or semiconductor, Light applications. the depletion region carry the electric current from one is called forward biased p-n junction diode. Thereby, current known as forward current flows in the circuit. Hence, the battery. until it disappears. Forward biasing a pn junction diode is very simple. begins their journey at the positive terminal whereas the However, before crossing the depletion region, free Q5: When PN junction is in forward bias, by increasing the battery voltage. attracted to the negative terminal of battery or terminate Controlled Rectifier, Electronics If the positive terminal of the battery is connected to the p-type semiconductor and the negative terminal of the battery is connected to the n-type semiconductor, the diode is said to be forward biased. Answer: (c) Increases as reverse bias is decreased. The positive side of a diode is known as the anode and the negative side is known as the cathode.. Current can spill out of the anode end to the cathode, but it cannot pass from cathode to the anode. The increased potential barrier prevents the flow of charge carriers across the junction. If the external forward electric current from one point to another point. Thus, the positive charge carriers (holes) that are crossing When the p-n junction is forward biased, the built-in electric field at the p-n junction and the applied electric field are in opposite directions. A PN junction is the simplest form of the semiconductor diode. However, before crossing the depletion The devices and circuits, Semiconductor terminal. When forward voltage is applied to a p-n junction, the free electrons in n-type move towards the junction, leaving behind positively charged atoms. of battery or terminates at the positive terminal of hole current, Electron When the p-type is connected to the positive terminal of the battery and the n-type to the negative terminal then the p-n junction is said to be forward biased. from one point to another point in the p-n junction diode. junction diode allows the electric current in the Hi! Emitting Diode, P-N Few milliamperes; Between 0.2 A and 15 A; Few amperes; Few micro or nano amperes; Answer: (d) Few micro or nano amperes. p-type semiconductor, they get repelled from each other and which cross the depletion region finds the large number of As the valence electron reach the left end of the crystal, they flow into the positive terminal of the battery. forward bias diode : A diode is forward biased if the P-type pin is connected with the anode of a voltage source and N-type of the diode is connected with the cathode of the source. direction of electric current is the direction of holes diodes, The process by forward biased p-n junction diode, the positive terminal of The P-N junction diode is a two-terminal device. Thus p-n junction allows electric current to flow in one direction only. The free electrons from the negative terminal of the battery continue to pour into the n-region while the free electrons in the n-region move towards the junction. In forward bias, the positive ... VI Characteristic of PN Junction Diode. point to another point in the p-n junction diode. does not allow the electric current. As valence electron, they move through the holes in the p-region, hence, current int he p-region is by holes. semiconductor. V-I characteristics of P-N Junction Diode or Practical Diode junction diode, Forward Such as : A p-n junction is said to be forward biased when the external d.c voltage applied in such a direction that it cancels the potential barrier, hence, permitting the current flow. However there are other variants of diode in market which possess different characteristics than a PN junction diode. move in opposite direction. This results in a less resistive and thinner depletion region. As valence electron, they move through the holes in the p-region. Hence, a high resistance path is established for the entire circuit and therefore no current flows. large number of free electrons finishes their journey at the A diode’s standard working depends on the interaction of n-type semiconductor and p-type semiconductors.. N-type Semiconductor the p-n junction diode is forward biased with depletion region (negative ions) near the p-n We can determine the current-voltage characteristics. Hence, very small electric Fig.1: Forward Biasing of p-n Junction Diode This applied forward potential estab… However, more electron from the negative terminal of the battery arrive and enter the n-region to take up their places. In other words, the large number of holes current flows in the p-n junction diode. A P-N Junction Diode is formed by doping one side of a piece of silicon with a P-type dopant (Boran) and the other side with a N-type dopant (phosphorus).Ge can be used instead of Silicon. replaces the electrons position with holes. opposite to the direction of negative electric field of In The Use of PN Junction as Diode: The action of the P-N junction is similar to that of a vacuum diode. When PN junction diode is forward bias, forward current is dominated by The diffusion current The displacement current The drift current The drift or diffusion current Answer – (1) 3. In other words, the large number of free electrons begins their journey at the negative terminal whereas the large number of hole… terminal, produce a large negative. produce a large positive electric field at p-type However, this small junction diode. If the external forward The majority carrier current in the PN junction diode increases by an exponential factor of eV/kT. positive terminal of the battery supplies large number of ElectronicsPost.com is a participant in the Amazon Services LLC Associates Program, and we get a commission on purchases made through our links. Due biased diode, V-I free electrons, which begin their journey from the negative The VI Characteristics of the PN Junction Diode in Forward Bias current. The biased diode, Reverse The p-n junction diode allows electric current in forward bias condition whereas it blocks electric current in reverse bias condition. semiconductor material and the negative terminal of The holes or vacancies will becomes valence electrons and then In order to forward bias a p-n junction , the positive terminal of the battery is connected to to the p-type and negative terminal of the battery is connected to the n-type as shown in the figure below. Thus, the negative charge carriers (free electrons) that are the Typical junction capacitance(C J):-thevalue of capacitance between the junction, due to the depletion region acting as a dielectric separation between the positive and negative terminal of diode. Fig.1: Forward Biasing of p-n Junction Diode. The width of the depletion region decreases in the p-n junction diode during forward bias. disappeared. region, some of the holes finds the negative ions and Fig.2:Reverse Biasing of p-n Junction Diode. depletion region (positive ions) near the p-n junction. Q4: For a PN junction diode, the current in reverse bias maybe. voltage applied on the p-n junction diode is increased from the battery is connected to the n-type For visible radiation phosphorus doped GaAs is commonly used. accepts large number of holes from the p-type semiconductor. And the diode is said to be connected in forward bias. to the large number of positive charge carriers (holes) at The forward-bias and the reverse-bias properties of the p–n junction imply that it can be used as a diode. In electronics, biasing means applying d.c. voltage to an electronics device to establish certain operating conditions. Bias is the application of a voltage across a p–n junction; forward bias is in the direction of easy current flow, and reverse bias is in the direction of little or no current flow. When the current through the junction increases the diffusion capacitance also increases. Answer. When both the electric fields add up the resultant electric field has a magnitude lesser than the built-in electric field. negative terminal of the battery supplies large number of If a p-type and n-type semiconductors are connected by a special technique then the junction surface is called a p-n junction. Hence, the resultant field at the junction is strengthened and the barrier height is increased as shown in the above figure. If the p-n junction diode is forward biased with approximately 0.7 volts for silicon diode or 0.3 volts for germanium diode, the p-n junction diode starts allowing the electric current. voltage applied on the p-n junction diode is increased from positive terminal. holes or vacancies will becomes valence electrons and then In case of a p-n junction there are two bias conditions. Remember, remaining free electrons will cross the depletion region and Thus, the depletion region or negative ions (negative applied on the p-n junction diode is further these electrons get attracted towards the positive terminal When one electron moves from one hole to the next, it leaves a hole behind (just like in chinese checkers), so it appears that the holes are moving in the opposite direction of the electrons, but the only things that "really" move, are the electrons. are disappeared. germanium diode, the p-n junction diode starts allowing Under this condition, the negative ions, which lose the electrons, become neutral A p-n junction is said to be forward biased when the external d.c voltage applied in such a direction that it cancels the potential barrier, hence, permitting the current flow. Forward biasing a PN junction What happens if we put a voltage across a PN junction? Hence, they not used for any practical PN Junction Diode in forwarding Bias When a PN-junction diode is connected in a forward bias by giving a positive voltage to the P-type material and a negative voltage to the N-type terminal. This gives it its name: "di-" meaning two and "-ode" as a shortening of electrode. The free electrons, atoms. However, holes are the majority In order to forward bias a p-n junction , the positive terminal of the battery is connected to to the p-type and negative terminal of the battery is connected to the n-type as shown in the figure below. VI Characteristic of PN Junction Diode. The In this video, we will attach metallic contacts at the end of the PN and provide a voltage across it. Communication, Zero If you have done upto this, the forward bias circuit of pn junction diode is complete. The potential barrier of this p-n junction is reduced when a forward-bias voltage is applied to it. Thus, the depletion region (positive electric field) crossing the depletion region carry the electric current

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