. This gives rise to very different behavior, depending upon the.. Therefore, diode is a PN junction. Diode has two terminals known as the anode (the P-type layer) This is achieved by changing the way of doping the PN junction and this reverse voltage is called the..
. The current in this biasing is low till breakdown is reached and hence the diode looks like an open circuit. When the input voltage of the reverse bias has reached the breakdown voltage, reverse current increases enormously.Electrical4U is dedicated to the teaching and sharing of all things related to electrical and electronics engineering.
The P-N junction diode appeared in the year 1950. It is the most essential and the basic building block of the electronic device. The PN junction diode is a two-terminal device, which is formed when one side of the PN junction diode is made with p-type and doped with the N-type material. The PN-junction is the root for semiconductor diodes. The various electronic components like BJTs, JFETs, MOSFETs (metal-oxide–semiconductor FET), LEDs and analog or digital ICs all supports semiconductor technology. The main function of the semiconductor diode is, it facilitates the electrons to flow totally in one direction across it. Finally, it acts as a rectifier. This article gives brief information about the PN junction diode, PN junction diode in forwarding bias and reverses bias and the VI characteristics of PN junction diode.When, V is positive the junction is forward biased, and when V is negative, the junction is reverse biased. When V is negative and less than VTH, the current is minimal. But when V exceeds VTH, the current suddenly becomes very high. The voltage VTH is known as the threshold or cut in voltage. For Silicon diode VTH = 0.6 V. At a reverse voltage corresponding to the point P, there is abrupt increment in reverse current. This portion of the characteristics is known as breakdown region. As shown in the figure, PN junction diode is a 2 terminal polarity sensitive device. Due to above fact, PN junction diode has many applications as outlined below. • It is used in clipping circuits as wave.. Summary: pn-Junction Diode Electrostatics. A depletion region (in which n and p are each much pn-Junction Reverse Breakdown. As the reverse bias voltage increases, the peak electric field in the..
Looking at the characteristic plot of the PN junction, it can be seen that in the forward direction (forward biased) it can be seen that very little current flows until a certain voltage has been reached. This represents the work that is required to enable the charge carriers to cross the depletion layer. This voltage varies from one type of semiconductor to another. For germanium it is around 0.2 or 0.3 volts and for silicon it is about 0.6 volts. The built in potential ( or barrier potential ) for pn junctions is given by following relation, Vbi = Vt ln(Na*Nd/ni²) which is normally of the order of 0.6V to 0.8 V. It can be seen that Vbi is purely function.. The working principle of a pn junction diode can be broadly understood under three categories: Unbiased pn Junction, Forward Biased pn Junction and Reversed Biased pn Junction. We will discuss each of them one by one.
. At positive terminal, all the free electrons will ends and all the holes will begins whereas at negative terminal all the free electrons will begins and all the holes will ends.The PN junction diode is the basic semiconductor diode format. It is used for many forms of rectification for current levels both large and small, as well as high and low voltage levels, and this semiconductor device finds many uses in all manner of electronic circuit designs.
A pn junction diode is a two terminal single crystal semiconductor device whose one side is doped with acceptors and other side by donors. Thus a pn junction is formed in diode The depletion region is very thin - often only few thousandths of a millimetre - but this is enough to prevent current flowing in the normal way. However it is found that different effects are noticed dependent upon the way in which the voltage is applied to the junction. PN Junction diode is a device made of two semiconductor material joined together with the required This results in the diffusion of aluminium into silicon and thus our PN junction diode is ready to be.. Why we represent VI characteristics only in 1 st and 3 Rd quaderents only?…….plz tell me sir……..
When this occurs the holes diffuse into the N-type area and a similar process occurs for the P-type material.Unbiasing means, no voltage source is connected across the terminals of pn junction diode. Let us investigate the phenomena happening inside the junction.The PN junction has the very useful property that electrons are only able to flow in one direction. As current consists of a flow of electrons, this means that current is allowed to flow only in one direction across the structure, but it is stopped from flowing in the other direction across the junction.When a PN junction diode is forward biassed, the anode is positive with resect to the cathode, and conversely, when reverse biassed the cathode is positive with respect to the anode. diode
Schottky Diodes: These diodes feature lower forward voltage drop as compared to the ordinary silicon PN junction diodes. The voltage drop may be somewhere between 0.15 and 0.4 volts at low currents.. The basic symbol of p-n junction diode under forward bias and reverse bias is shown in the below figureOne electrode of the semiconductor device is termed the anode and the other is termed the cathode. For a current to flow across the PN diode junction it must be forward biased. Under these conditions conventional current flows from the anode to the cathode, but not the other way around.
27 Ideal Diode Model of pn Diode Circuit symbol I-V characteristic Switch model ID ID (A) ID + VD - + VD - forward bias reverse bias VD (V) An ideal diode passes current only in one direction To summarize, a forward biased diode acts like a closed switch provided the forward biasing voltage must be greater than the barrier potential. If the forward biasing voltage is less than the barrier potential, the energy imparted by battery to the electrons and holes will not be enough energy to cross the pn junction. Hence it will block the flow of current. Thus we observe that a diode not a bilateral device. Note that bilateral device is once which allows the flow of current in both the direction.Due to this barrier potential, work needs to be done for bring a hole from p side to n side. Similar is the case for electron. If barrier potential is assumed to be VB, then the work required to be carried out for bringing a hole from p side to n side will be equal to eVB. Thus we observe that there exists a barrier potential across the pn junction of diode. So we must be able to measure this by using voltmeter? If you ever try to measure this voltage by connecting the lead of voltmeter across the diode terminals, you will get zero reading. Isn’t it a contradiction? It is true that there exists a barrier potential, but at the same time it is also true that there exists a contact voltage drop between the semiconductor and metal contact. The barrier potential is exactly balanced by the contact potential at the metal-semiconductor contacts at the ends of diode terminals. This is the reason, the voltmeter is unable to measure the barrier potential of diode.
As shown in the figure, PN junction diode is a 2 terminal polarity sensitive device. Due to above fact, PN junction diode has many applications as outlined below. • It is used in clipping circuits as wave.. In forward biased p-n junction diode (p-type connected to positive terminal and n-type connected to negative terminal), anode terminal is a positive terminal whereas cathode terminal is negative terminal.. In the zero bias junction, potentially provides higher potential Therefore, this is all about PN junction diode in zero bias, forward bias and reverse bias conditions..
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3. SOD. small outline diode. 2. SOIC PN junction diode parameters like reverse saturation current, bias current, reverse breakdown voltage and barrier voltage are dependent on temperature. Mathematically diode current is given byI=IS∗(exp.. Note 3. PW = 100µs, Duty Cycle = 2%. Note 4. Irradiance from a Light Emitting Diode (LED) can be calculated by: I H = e2 d where H is irradiance in mW/cm2 Ie is radiant intensity in mW/steradian d2 is.. What are Diodes? - Types of Diodes - Applications of Diodes - PN Junction Diode - Construction - Working - Forward Bias, Reverse Bias and their significance. pn-Übergang an äußerer Spannung. Im Folgenden wird das Funktionsprinzip einer Halbleiterdiode erklärt Diode in Sperrrichtung Wird die Diode in Sperrrichtung betrieben, so liegt die p-Schicht am..
Справочник по импортным диодам.. If, we apply forward bias voltage to the p-n junction diode. That means if the positive side of the battery is connected to the p-side, then the depletion regions width decreases and carriers (holes and free electrons) flow across the junction. If we apply a reverse bias voltage to the diode, the depletion width increases and no charge can flow across the junction.When the +Ve voltage is applied to the N-type material, then it attracts the electrons near the positive electrode and goes away from the junction, whereas the holes in the P-type end are also attracted away from the junction near the negative electrode.Today, the PN junction has undergone a significant amount of development. Many varieties of diode are in use in a variety of applications. In addition to this, the PN junction forms the basis of much of today's semiconductor technology where it is used in transistors, FETs, and many types of integrated circuit. 149 pn diode products are offered for sale by suppliers on Alibaba.com, of which integrated circuits Pn diode products are most popular in United Kingdom, United States, and Russian Federation
PN junction diodes can be obtained in a number of semiconductor materials - the earliest diodes tended to be made from germanium, but most of them today are silicon diodes. principle operation of PN JUNCTION Diode by Annie,RMKEC. This video explains about the various concepts related with diodes through solving various diode associated numerical problems In the step-recovery diode the doping level is gradually decreased as the junction is approached. This reduces the switching time since the smaller amount of stored charge near the junction can be.. Diode. a semiconductor device with terminals , typically allowing the flow of current in one direction only. Diodes and transistors as well as certain special types of electronic devices
The basis portion is a general description of the p-and n-type semiconductor , and the pn junction to be found. A semiconductor diode is a bipolar device.. 3. Diodes and Diode Circuits. TLT-8016 Basic Analog Circuits. If the reverse-biasing voltage is sufficiently large the diode is in reverse-breakdown region and large current flows though it If the p-n junction diode is reverse biased, it blocks the electric current flow. Under reverse biased condition, the p-type semiconductor is connected to the negative terminal of battery whereas; the n-type semiconductor is connected to the positive terminal of battery.
If we apply a reverse bias to the PN-junction diode, that means the positive terminal is connected to the N-type material and the negative terminal is connected to the P-type material across the diode which has the effect of increasing the width of the PN junction diode and no charge can flow across the junction Electronic Devices and Circuits Questions and Answers - PN Diode Switching Times. 1. Diode acts as a short circuit when switched from forward to reverse bias for some time due to_ a).. Volt-ampere (V-I) characteristics of a pn junction or semiconductor diode is the curve between voltage across the junction and the current Fig.1: Circuit Connection for V-I characteristics of a pn junction
Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased Should Customers purchase or use Diodes Incorporated products for any unintended or.. pn junction diode conducts current in one directions where as the zener diode conducts in both the I don't think that the pn junction diode can emit light. Maybe it does, but a 'plastic' that covering the.. Diode ＜Types of Diodes＞ : This page introduces various diodes such as Rectification Diode, Switching Diode Diode ＜Types of Diodes＞. Rectification Diode (REC): Structure and Features
Now Playing. Lecture 22: PN Junction, Di.. Standard PN diodes conduct far less in a reverse bias condition than Shottkey diodes. Shottkey diodes have a much lower capacitance which is why they're used in SMPS applications, but if you want a blocking diode and can tolerate the larger forward voltage drop, the standard PN diode is the way to go.Signal diodes also have many uses in processing signals in electronic equipment; they are used to obtain the audio and video signals from transmitted radio frequency signals (demodulation) and can also be used to shape and modify AC signal waveforms (clipping, limiting and DC restoration). Diodes are also built into many digital integrated circuits to protect them from dangerously large voltage spikes. Diodes Cathode terminal or positive terminal supplies holes to the p-n junction. In other words, cathode terminal is the source of holes, the holes begins their journey at positive or cathode terminal and occupies the electrons position in the n-type semiconductor. The free electrons in the n-type semiconductor gets attracted towards the positive terminal. The holes from the positive terminal cannot move towards the negative terminal because the wide depletion region at the p-n junction opposes the flow of holes.
This circuit shows how the anode of the diode is positive with respect to cathode and the cathode is connected to the output which is positive with resect to the zero volt line. In this way the voltage polarities around the circuit are maintained.Therefore, this is all about PN junction diode in zero bias, forward bias and reverse bias conditions and VI characteristics of PN junction diode. We hope that you have got a better understanding of this concept. Furthermore, any doubts regarding this article, or electronics projects please give your feedback by commenting in the comment section below. Here is a question for you, which diode is used in the phototransistor?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. If the external voltage becomes more than the value of the potential barrier (estimate 0.7 V for Si and 0.3V for Ge, the opposition of the potential barriers will be overcome and the flow of current will start.Because the negative voltage repels electrons near to the junction by giving them the energy to combine and cross over with the holes being pushed in the opposite direction to the junction by the positive voltage.Where the two areas meet and at equilibrium there are no free holes or electrons. This means that there are no available charge carries in this region. In view of the fact that this area is depleted of charge carriers it is known as the depletion region.The diode is simple in its basic concept, being formed from the junction of N-type and P-type materials, although in reality the manufacture and theory of operation are more complex.
If the p-n junction diode is forward biased, it allows the electric current flow. Under forward biased condition, the p-type semiconductor is connected to the positive terminal of battery whereas; the n-type semiconductor is connected to the negative terminal of battery. Відео, які сподобалися. Популярне. Pn diode. EduPoint. 3.Pn junction diode| jee-neet physics class 12. 2 роки тому
This means that when a diode is used in a circuit like a rectifier, the cathode is provides the positive output - the anode still remaining more positive as shown in the circuit below.The potential difference across the PN junction is maintained constant by the depletion layer action. The max amount of current to be conducted is kept incomplete by the load resistor because when the PN junction diode conducts more current than the normal specifications of the diode, the extra current results in the heat dissipation and also leads to serving damage to the device.
When connect Voltage source's Polarities the same with Diode's Polarities . Diode does not conduct . No current can flow. When connect Voltage source's Polarities different with Diode's Polarities . Diode conducts . current can flow. Diode does not conduct current with voltage below Conducting Voltage As the voltage applied between anode and cathode increases, forward current increases slowly at first, as charge carriers begin to cross the depletion layer then increasing rapidly in an approximately exponential manner. The resistance of the diode, when ‘turned on’ or conducting in a ‘forward biased’ mode is therefore not zero ohms, but is very low. Because forward conduction increases after the depletion potential is overcome in an approximately following exponential curve, forward resistance (V/I) varies slightly depending on the voltage applied. Semiconductor diode is a type of diode, which contains p-n junction made from differently doped Semiconductor Diode - Current-voltage characteristic. How to determine where is the anode and.. The result of this in a characteristic curve of zero current flowing up to built-in potential is called as “knee current” on the static curves & then a high current flow through the diode with a slight increase in the external voltage as shown below. The PN junction diode is used for rectification purpose because it allows the current to flow only in one direction. It is a type of switch which only allows the forward current to pass through it
Introductio to Semiconductor Diodes, silicon diode construction. How diodes work and diode characteristics. Silicon PN junction diodes have a junction potential of about 0.6V to 0.7V Accordingly the different areas of the semiconductor have different properties. The N-type semiconductor has an excess of electrons whilst the P-type has an excess of holes.
The V-I characteristic of SCR, MOSFET, LED, PN junction diode, and Zener diode is The diode, for example, has varying resistance for different values of voltage. However, it has a linear characteristic.. - What are Diodes? - Types of Diodes - Applications of Diodes - PN Junction Diode - Construction - Working - Forward Bias, Reverse Bias and their significance - Characteristics of Diodes - Zener Diode
The PN junction is one of the most important structures in today's electronics scene. It forms the basis of most of today's semiconductor technology, and was the first semiconductor device to be used.When a PN junction diode is connected in a Reverse Bias condition, a positive (+ Ve) voltage is connected to the N-type material & a negative (-Ve) voltage is connected to the P-type material. PN Junction Diode and Diode Characteristics. 494 x 317 gif 7kB. thejargonweb.wordpress.com. www.electronics-tutorials.ws. PN Junction Diode and Diode Characteristics Like any diode, the PN junction diode has two connections or electrodes. This gives it its name: "di-" meaning two and "-ode" as a shortening of electrode.
PN Junction Under Bias -In this module on pn junction under bias, we will cover the following topics Reviews for Coursera's Diode - pn Junction and Metal Semiconductor Contact Based on 0 reviews PN Junction diodes are made by doping the trivalent element into one side of an intrinsic semiconductor like silicon and doping pentavalent to another side of it PN-Junction Diode. The following table contains the model parameters for the pn-junction diode model. Name. Symbol A pn junction diode is said to be reverse biased if the positive plate of battery is connected to the n side and negative plate to the p side. A reverse biased diode is shown in figure below.
Menu MCQBasics Basic ElectricalCircuit TheoryElectrical LawsEngineering MaterialsBatteriesIlluminationPhysicsPower Systems GenerationTransmissionDistributionSwitchgearProtectionMeasurementControl SystemsUtilitiesSafetyMachines TransformersElectric MotorsGeneratorsElectrical DrivesElectronics Electronics DevicesPower ElectronicsDigital ElectronicsBiomedicalTools Resistor Color CodeOhm’s Law CalculatorVoltage Divider CalculatorParallel Resistor CalculatorTransformer Calculator Menu MCQBasics Basic ElectricalCircuit TheoryElectrical LawsEngineering MaterialsBatteriesIlluminationPhysicsPower Systems GenerationTransmissionDistributionSwitchgearProtectionMeasurementControl SystemsUtilitiesSafetyMachines TransformersElectric MotorsGeneratorsElectrical DrivesElectronics Electronics DevicesPower ElectronicsDigital ElectronicsBiomedicalTools Resistor Color CodeOhm’s Law CalculatorVoltage Divider CalculatorParallel Resistor CalculatorTransformer Calculator PN Junction Diode and Characteristics of PN Junction DiodeJanuary 29, 2019February 24, 2012 by Electrical4U PN junction diode is one of the fundamental elements in electronics. 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 PN junction diode is a two-terminal electronics element, which can be classified as either ‘step graded’ or ‘linear graded’.Once the voltage applied to the anode is made more positive than the cathode by an amount greater than the depletion layer potential, forward conduction from anode to cathode conventional current commences, as shown in Fig. 2.0.5.The formation of pn junction in a single crystal due to doping with p type and n type material is shown in figure below.Understanding Voltage Regulator ICs How to use Bridge Rectifier IC? How to identify Terminals? Comparison between Synchronous Motor and 3-Phase Induction Motor 555 Timer Project Ideas - Relay, LED, Lamp Driver Circuits Are we missed any point?... Please share in the comments.... It is easy to determine the polarity of many wired diodes. The "bar" on the circuit symbol corresponds to the cathode of the diode and this is often marked by a white line around the circumference of the actual diode. Orientation for SMD diodes is less obvious and is normally determined as a result of the fact that diodes are contained in a similar package to transistors having three terminals - only two are used for the SMD diodes, but they can only be orientated in one direction.
In the above figure, arrowhead of a diode indicates the conventional direction of electric current when the diode is forward biased (from positive terminal to the negative terminal). The holes which moves from positive terminal (anode) to the negative terminal (cathode) is the conventional direction of current.The axes of the graph show both positive and negative values and so intersect at the centre. The intersection has a value of zero for both current (the Y axis) and voltage (the X axis). The axes +I and +V (top right area of the graph) show the current rising steeply after an initial zero current area. This is the forward conduction of the diode when the anode is positive and cathode negative. Initially no current flows until the applied voltage exceeds the forward junction potential. After this, current rises steeply in an approximately exponential manner. Real Diode Characteristics. Ideally, diodes will block any and all current flowing the reverse direction, or just act like a short-circuit if current flow is forward. Unfortunately, actual diode behavior isn't quite..
The operation of diodes, as described above, can also be described by a special graph called a ‘characteristic curve’. This graphs shows the relationship between the actual currents and voltages associated with the different terminals of the device. An understanding of these graphs helps in understanding how the device operates.When the diode is reverse biased (the anode connected to a negative voltage and the cathode to a positive voltage), as shown in Fig. 2.0.6, positive holes are attracted towards the negative voltage on the anode and away from the junction. Likewise the negative electrons are attracted away from the junction towards the positive voltage applied to the cathode. This action leaves a greater area at the junction without any charge carriers (either positive holes or negative electrons) as the depletion layer widens. Because the junction area is now depleted of charge carriers it acts as an insulator, and as higher voltages are applied in reverse polarity, the depletion layer becomes wider still as more charge carriers away from the junction. The diode will not conduct with a reverse voltage (a reverse bias) applied, apart from a very small ‘Reverse Leakage Current’ (IR), which in silicon diodes is typically less than 25nA. However if the applied voltage reaches a value called the ‘Reverse Breakdown Voltage’ (VRRM) current in the reverse direction increases dramatically to a point where, if the current is not limited in some way, the diode will be destroyed.The free electrons are attracted towards the anode terminal or positive terminal whereas the holes are attracted towards the cathode terminal or negative terminal. Schokky diode: Use of (normally) P-doped silicon bonded to metal. The junction effect is at the metal connection and it is because only one doped-tpye of silicon is used you end up with the lower on-state Generally, terminal refers to a point or place at which any object begins or ends. For example, bus terminal or terminus is a place at which all the buses begins or ends. Similarly, in a p-n junction diode, terminal refers a point at which charge carriers begins or ends.
Diodes are one of the simplest, but most useful of all semiconductor devices. Many types of diode are used for a wide range of applications. Rectifier diodes are a vital component in power supplies where they are used to convert AC mains (line) voltage to DC. Zener diodes are used for voltage stabilisation, preventing unwanted variations in DC supplies within a circuit, and to supply accurate reference voltages for many circuits. Diodes can also be used to prevent disastrous damage to battery powered equipment when batteries are connected in the wrong polarity.Modern silicon diodes are generally produced using one of various versions of the planar process, also used for manufacturing transistors and integrated circuits. The layered construction used in Silicon Planar methods give a number of advantages such as predictable performance and reliability as well as being advantageous to mass production. dual hi speed sw diode 50V 0.15A. BCR08PN. Infineon
A reverse biased pn junction diode acts like an open switch and blocks the flow of current from anode to cathode.Anode terminal is a positively charged electrode or conductor, which supplies holes to the p-n junction. In other words, anode or anode terminal or positive terminal is the source of positive charge carriers (holes), the positive charge carriers (holes) begins their journey at anode terminal and travel through the diode and ends at cathode terminal. For a PN junction diode, the total potential across the semiconductor equals the built-in potential minus the applied voltage
Pl. Pm. Pn pn-juntion-Diode At Thermal Equilibrium A short time after the junction is established and thermal pn-juntion-Diode Energy Band Diagram at Thermal Equilibrium At thermal equilibrium. dE f =0 dx i.e..
High Performance N-Channel POWERJFETTM with PN Diode. A PN Diode is added for. applications where a freewheeling diode is required. This product has tin plated leads Diode, an electrical component that allows the flow of current in only one direction. The most common type of diode uses a p-n junction in which one material (n) has electrons as charge carriers.. There are three possible biasing conditions and two operating regions for the typical PN-Junction Diode, they are zero bias, forward bias and reverse bias. PN Junction Diode - Mcqs/Notes/IQs. Home » Electronics Engineering » Physical Electronics » PN Junction Diode This reverse current results from what are called minority carriers. These are a very small number of electrons found in a P type region or holes in an N type region. Early semiconductors has relatively high levels of minority carriers, but now that the manufacture of semiconductor materials is very much better the number of minority carriers is much reduced as are the levels of reverse currents.
In a step graded PN junction diode, the concentration of dopants both, in the N side and the P side are uniform up to the junction. But in a linearly graded junction, the doping concentration varies almost linearly with the distance from the junction. When we do not apply any voltage across the PN diode, free electrons will diffuse through the junction to P side and holes will diffuse through the junction to N side and they combine with each other. Having the diode work properly requires a process known as doping. A diode (PN junction) in an electrical circuit allows current to flow more easily in one direction than another Find here details of pn junction diode manufacturers, pn-junction diode suppliers, dealers, traders & exporters from India. Buy pn junction diode through verified companies with product rating
A pn junction is said to be formed only when a bonding force is created between the P-type and N-type Diodes - What Are Diodes - PN Junction - Forward Bias - Reverse Bias - Zener Diodes.. Even it its basic form as a diode, this electronic component is used in enormous quantities, but beyond that, the PN junction forms the bedrock of most of today's high-tech transistors, integrated circuits and other semiconductor devices. Without the PN junction, life today would be very different, and electronics would be a very different scene.Cathode is the negatively charged electrode or conductor, which supplies free electrons to the p-n junction. In other words, cathode terminal or negative terminal is the source of free electrons, the negative charge carriers (free electrons) begins their journey at cathode terminal and travel through the diode and ends at anode terminal.
Diode Tutorial Includes: Diode types Diode specs & ratings PN junction diode LED PIN diode The PN junction diode is the basic semiconductor diode format. It is used for many forms of rectification.. Diode Tutorial Includes: Diode types Diode specs & ratings PN junction diode LED PIN diode Schottky barrier diode Varactor / varicap Zener diode After resistors and capacitors, one of the most widely used electronic components is the PN junction diode. Présentation au sujet: DIODES DIODE A JONCTION PN DIODE ZENER DIODES ELECTROLUMINESCENTES LED— Transcription de la présentatio Analog Electronics: V-I Characteristics of PN Junction Diode Topics Covered: 1. Volt-ampere characteristics of diode in forward bias condition
But the flow of minority carrier i.e. electrons in p side and holes in n side remain unaffected. It should be noted that the concentration of minority carrier is dependent on the temperature. These are thermally generated minority carrier in p and n side. Due to flow of minority carrier across the junction, a small current flows from cathode to anode. This current is called Reverse Saturation Current. Value of reverse saturation current is independent of reverse bias voltage but dependent on junction temperature. Its value increases with increase in junction temperature. The flow of reverse saturation current Is is shown in above figure. The first semiconductor diode to be used was the Cat's Whisker wireless detector used in early wireless sets. It consisted of a wire placed onto a material that was effectively a semiconductor. The point where the wire met the semiconductor then formed a small PN junction and this detected the radio signals. It was actually a form of Schottky diode, but nevertheless the earliest form of PN junction and semiconductor device. PN junction diode is one of the fundamental elements in electronics. In a step graded PN junction diode, the concentration of dopants both, in the N side and the P side are uniform up to the junction The diode can be thought of consisting of the two areas being brought into intimate contact with each other.In the reverse direction, a perfect diode would not allow any current to flow. In reality a small amount of current does flow, although this is likely to be very small and in the region of pico amps or microamps. It has been exaggerated on the diagram so that it can be seen. Although it is normally very low, the performance of any diode will degrade at higher temperatures and it is also found that germanium is not as good as silicon.
Due to its characteristics and biasing we use it as the PN diode which we use in the different circuit. How we use it and what are the advantages we will discuss further A PN junction is typically made from a single piece of semiconductor that has two differing areas: one is made to be P-type and the other N-type. 14.1 A PN diode, forward biased, with current flowing. Black dots are electrons, and circles are Figure 17 Transient current induced in SOI pn junction diode by 15-MeV C-ion irradiation (solid line) The free electrons moving from negative terminal (cathode) to the positive terminal (anode) actually carry the electric current. However, due to the convention we have to assume that the current direction is from positive terminal to the negative terminal.