Diode Topics Complete Notes PDF

9/4/2024 1 9/4/2024 2 9/4/2024 3 9/4/2024 4  HANDOVER THE TITLE OF PROJECT(CA3) CONDITIONS- - ARDUINO BASED PROJECT only - SAME TITLE NOT ALLOWED FOR OTHER GROUP - MAXIMUM 4 STUDENT IN GROUP, handover Group project title, first come on first basis - Project Rep...

9/4/2024 1 9/4/2024 2 9/4/2024 3 9/4/2024 4  HANDOVER THE TITLE OF PROJECT(CA3) CONDITIONS- - ARDUINO BASED PROJECT only - SAME TITLE NOT ALLOWED FOR OTHER GROUP - MAXIMUM 4 STUDENT IN GROUP, handover Group project title, first come on first basis - Project Report Common for Group(single common copy) - On Saturday, you may discus any issue/points regrading Project 9/4/2024 5 9/4/2024 6 9/4/2024 7 9/4/2024 8 9/4/2024 9 9/4/2024 10 IN CASE, ANY STUDENT, WHO IS NOT ABLE TO DOWNLOAD AND INSTALL PROTEUS ON YOUR LAPTOP, YOU COME WITH PENDERIVE, collect softcopy AND RUN & INSTALL ON YOUR OPERATING SYSTEM OR LAPTOP 9/4/2024 11 9/4/2024 12 9/4/2024 13 BASIC ABOUT CONDUCTOR , SEMICONDUCTOR and INSULATOR 9/4/2024 14 9/4/2024 15 9/4/2024 16 9/4/2024 17 9/4/2024 18 9/4/2024 19 9/4/2024 20 9/4/2024 21 9/4/2024 22 n-Type Semiconductors N-type semiconductors are extrinsic semiconductors in which dopant atoms can provide additional conduction electrons to the host material (e.g. phosphorus in silicon). p-Type Semiconductors To enhance the number of free charge carriers, a p-type (p for “positive”) semiconductor is formed by adding a certain type of atom to the semiconductor. The goal of p-type doping is to produce a large number of holes. 9/4/2024 23 9/4/2024 24 9/4/2024 25 9/4/2024 26 9/4/2024 27  MAIN USE OF PN JUNCTION DIODE A p-n junction diode is used for passing the current in one direction. It is a two-terminal or two electrode semiconductor device. This diode helps in stopping the current in the reverse or opposite direction. 9/4/2024 28  Characteristics- PN Junction Diode A PN Junction Diode is one of the simplest semiconductor devices around, and which has the electrical characteristic of passing current through itself in one direction only. Unlike a resistor, a diode does not behave linearly with respect to the applied voltage. 9/4/2024 29 9/4/2024 30 9/4/2024 31 9/4/2024 32 9/4/2024 33 9/4/2024 34  Principle of PN junction diode A p–n junction diode allows charge carriers to flow in one direction, but not in the opposite direction Negative charge carriers (electrons) can easily flow through the junction from n to p but not from p to n, and the reverse is true for positive charge carriers (holes). 9/4/2024 35 9/4/2024 36 9/4/2024 37 Applications of P-N Junction Diode It can be used as a solar cell. When the diode is forward-biased, it can be used in LED lighting applications. It is used as rectifier in many electric circuits and as a voltage-controlled oscillator in varactors. 9/4/2024 38 9/4/2024 39  -in electrical switches and are used in surge protectors because they can prevent a spike in the voltage. Diodes are used in circuit protection due to their ability to restrict electrical current to flow in only one direction. This trait is useful because some electrical components and devices will be damaged or malfunction if current flows in the wrong direction. 9/4/2024 40  LEDs are used in sensors and laser devices. Zener diodes are used as voltage regulators. Diodes help in performing digital logic. Diodes are useful in the construction of logic gates, which are the building blocks of digital electronics. one can create gates that perform basic logical functions like AND, OR, and NOT. 9/4/2024 41 Advantages of P-N Junction Diode To convert alternating current (AC) to direct current (DC), a p-n junction diode can be used (DC). These diodes are found in power supplies. If the diode is forward biased, current can flow. However, if it is reverse biased, it prevents current flow. 9/4/2024 42  Disadvantages of pn junction diode -PN junction diode don't work in reverse biased mode. -It can be overstressed during breakdown in voltage referencing. -May cause delay in high-scale operations. 9/4/2024 43  The PN Junction Metallurgical Steady State Na Junction Nd - - - - - + + + + + When no external source P - - - - - + + + + + is connected to the pn n - - - - - + + + + + junction, diffusion and - - - - - + + + + + Space Charge drift balance each other ionized acceptors Region ionized out for both the holes donors E-Field and electrons _ _ + + h+ drift = h+ diffusion e- diffusion = e- drift Space Charge Region: Also called the depletion region. This region includes the net positively and negatively charged regions. The space charge region does not have any free carriers. The width of the space charge region is denoted by W in pn junction formula’s. Metallurgical Junction: The interface where the p- and n-type materials meet. Na & Nd: Represent the amount of negative and positive doping in number of carriers per centimeter cubed. Usually in the range of 1015 to 1020. 9/4/2024 44  The Biased PN Junction Metal Contact “Ohmic Contact” _ + (Rs~0) Applied P Electric Field n I _ + Vapplied The pn junction is considered biased when an external voltage is applied. There are two types of biasing: Forward bias and Reverse bias. 9/4/2024 These are described on then next slide. 45  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 positive voltage is applied to the P-type material. If this external voltage becomes greater than the value of the potential barrier, approx. 0.7 volts for silicon and0.3voltsfor germanium, the potential barriers opposition will be overcome and current will start to flow. This is because the negative voltage pushes or repels electrons towards the junction giving them the energy to cross over and combine with the holes being pushed in the opposite direction towards the junction by the positive voltage. This results in a characteristics curve of zero current flowing up to this voltage point, called the knee on the static curves and then a high current flowthrough the diode with little increase in the external voltage as shown below. 9/4/2024 46  When a diode is connected in a Forward Bias condition, a negative voltage is applied to the N-type material and a positive voltage is applied to the P-type material. If this external voltage becomes greater than the value of the potential barrier, approx. 0.7 volts for silicon and0.3voltsfor germanium, the potential barriers opposition will be overcome and current will start to flow. This is because the negative voltage pushes or repels electrons towards the junction giving them the energy to cross over and combine with the holes being pushed in the opposite direction towards the junction by the positive voltage. 9/4/2024 47  Reverse Biased PN Junction Diode When a diode is connected in a Reverse Bias condition, a positive voltage is applied to the N-type material and a negative voltage is applied to the P-type material. The positive voltage applied to the N-type material attracts electrons towards the positive electrode and away from the junction, while the holes in the P-type end are also attracted away from the junction towards the negative electrode. The net result is that the depletion layer grows wider due to a lack of electrons and forms a potential barrier which prevent the current from flowing through the semiconductor material. 9/4/2024 48 9/4/2024 49 9/4/2024 50 9/4/2024 51 9/4/2024 52  PN Junction Breakdown An electrical breakdown of any material such as the conductor, semiconductor, and insulator can occur due to two different phenomena known as a) Zener Breakdown b) Avalanche Breakdown. 9/4/2024 53 9/4/2024 54  Zener Breakdown When the reverse bias voltage is applied across the pn terminals, the depletion region begins to increase. As a result, more electrons and holes are generated. These electrons and holes produce a very powerful electric field across the junction of the diode. The magnitude of the electric field will depend on the magnitude of the applied reverse voltage. The electric field exerts an electron force which is present in the valence band. This will enter the conduction band, and the conduction process begins. This phenomenon is called Zener breakdown. 9/4/2024 55  Avalanche breakdown The free electrons move across the depletion region of the diode. They possess velocity, and the electrons acquire kinetic energy. Due to the presence of velocity, the minority carriers randomly move inside the diode. It collides with stationary electrons held to the atom by covalent bonding. The covalent bonding gets broken by bound electrons, and the conduction process begins. The electrons transfer the kinetic energy to stationary electrons which makes them move. As the magnitude of the reverse bias voltage increases, the energy rises. The resulting collision produces a current, which causes the breakdown of the diode. This breakdown is called an avalanche breakdown. 9/4/2024 56 DIFFERENCE BETWEEN ZENER AND AVALANCHE BREAKDOWN 9/4/2024 57  Properties of Diodes The Shockley Equation The transconductance curve on the previous slide is characterized by the following equation: ID = IS(eVD/VT – 1) As described in the last slide, ID is the current through the diode, IS is the saturation current and VD is the applied biasing voltage. VT is the thermal equivalent voltage and is approximately 26 mV at room temperature. The equation to find VT at various temperatures is: VT = kT q k = 1.38 x 10-23 J/K T = temperature in Kelvin q = 1.6 x 10-19 C  is the emission coefficient for the diode. It is determined by the way the diode is constructed. It somewhat varies with diode current. For a silicon diode  is around 2 for low currents and goes down to about 1 at higher currents 9/4/2024 58 9/4/2024 59  Types of Diodes and Their Uses PN Junction Are used to allow current to flow in one direction Diodes: while blocking current flow in the opposite direction. The pn junction diode is the typical diode that has been used in the previous circuits. A K P n Schematic Symbol for a PN Representative Structure for Junction Diode a PN Junction Diode Zener Diodes: Are specifically designed to operate under reverse breakdown conditions. These diodes have a very accurate and specific reverse breakdown voltage. A K Schematic Symbol for a 9/4/2024 Zener Diode 60  Types of Diodes and Their Uses Light-Emitting Light-emitting diodes are designed with a very large Diodes: band gap so movement of carriers across their depletion region emits photons of light energy. Lower band gap LEDs (Light-Emitting Diodes) emit infrared radiation, while LEDs with higher band gap energy emit visible light. Many stop lights are now starting to use LEDs because they are extremely bright and last longer than regular bulbs for a relatively low cost. The arrows in the LED A K representation indicate emitted light. Schematic Symbol for a Light-Emitting Diode 9/4/2024 61  Types of Diodes and Their Uses Photodiodes: While LEDs emit light, Photodiodes are sensitive to received light. They are constructed so their pn junction can be exposed to the outside through a clear window or lens. A K In Photoconductive mode the saturation current increases in proportion to the intensity of the received light. This type of diode is used in CD  players. A K In Photovoltaic mode, when the pn junction is exposed to a certain wavelength of light, the diode Schematic Symbols for generates voltage and can be used as an energy Photodiodes source. This type of diode is used in the production of solar power. 9/4/2024 62 9/4/2024 63 9/4/2024 64 PIECEWISE LINEAR EQUIVALENT MODEL 9/4/2024 65 9/4/2024 66 A piecewise linear model of a diode is an approximate representation of the diode's current-voltage (I-V) characteristic using a series of linear segments. This model simplifies the complex non-linear behavior of a diode and allows for easier analysis and modeling in circuit design. The piecewise linear model typically consists of three main regions: Forward-bias region: In this region, the diode exhibits a relatively low voltage drop (typically around 0.7V for silicon diodes) as the current increases. This region can be modeled as a constant voltage source in series with a small resistance. Reverse-bias region: In this region, the diode behaves like an open circuit, allowing negligible current to flow until the reverse breakdown voltage is reached. The reverse-bias region is often modeled as an infinite resistance. Breakdown region: Beyond the reverse breakdown voltage, the diode enters the breakdown region, where a rapid increase in current occurs. This region is typically modeled as a constant voltage source in series with a small resistance. 9/4/2024 67 WHAT YOU LEARNED FROM VI CHACTERSTICS OF PN JUNCTION DIODE ? 9/4/2024 68 WHAT YOU LEARN FROM VI CHACTERSTICS OF PN JUNCTION DIODE PN junction diode conducts current only in one direction – i.e. during forward bias. During forward bias, the diode conducts current with an increase in voltage. During reverse bias, the diode does not conduct with an increase in voltage. 9/4/2024 69 9/4/2024 70  MCQ Question-2 During reverse bias, a small current develops known as a) Forward current b) Reverse current c) Reverse saturation current d) Active current 9/4/2024 71  Answer:C When the diode is reverse biased, a small current flows between the p-n junction which is of the order of the Pico ampere. This current is known as reverse saturation current. 9/4/2024 72 MCQ Question -3 When the diode is reverse biased with a voltage of 6V and Vbi=0.63V. Calculate the total potential. a) 6V b) 6.63V c) 5.27V d) 0.63V 9/4/2024 73 Answer: b Explanation: Vt=Vbi+VR =0.63+6 =6.63V. 9/4/2024 74 What will be the output of the following circuit? (Assume 0.7V drop across the diode) The output of the following circuit is 11.3V a) 12V b) 12.7V c) 11.3V d) 0V 9/4/2024 75 Answer: c V=12-0.7 =11.3V. 9/4/2024 76 MCQ, Question-5 How many junction/s do a diode consist? a) 0 b) 1 c) 2 d) 3 9/4/2024 77  Answer:B Explanation: Diode is a one junction semiconductor device which has one cathode and anode. The junction is of p-n type. 9/4/2024 78  Practical work 9/4/2024 79 The 1N4001 diode belongs to the family of the 1N400x diode series, which are most commonly used in household electronic appliances. It allows the flow of current only in one direction, that is from anode terminal to cathode terminal just like a normal diode. It is referred to as a general-purpose rectifier diode used for rectification purposes. The 1N4001 diode is shown in the figure below. The current carrying capacity is of maximum 1 Ampere and can tolerate up to a peak value of 30 Amps. This type of silicon diode is mainly used in designing circuits with less than 1 Ampere. The negligible reverse current is 5 microAmps. The reverse peak voltage, where the diode can withstand is up to a maximum of 50 Volts. 9/4/2024 80  Features & Specifications The average forward current of 1N4001 diode is 1 Ampere The RMS reverse voltage is 35 Volts The reverse current is 5 microAmps The peak repetitive reverse DC voltage is 50 Volts The maximum forward voltage is 1.1 Volts. The maximum reverse current is 10 microAmps It operates at -55 to +175°C maximum temperature ranges The maximum output current will be 1 Amp. The maximum reverse voltage and DC voltage rating is 50 Volts The maximum power dissipation is 3 Watts. 9/4/2024 81 9/4/2024 82 9/4/2024 83  VIRTUAL LAB LINK FOR PN JUNCTION DIODE PRACTICAL http://vlabs.iitkgp.ernet.in/be/exp5/forwardbiaseddiode_si.html 9/4/2024 84 9/4/2024 85 9/4/2024 86 Numerical PROBLEM on DIODE 9/4/2024 87  Numerical PROBLEM-1 Calculate the forward bias current of a Si diode when forward bias voltage of 0.4V is applied, the reverse saturation current is 1.17×10-9A and the thermal voltage is 25.2mV. a) 9.156mA b) 8.23mA c) 1.256mA d) 5.689mA 9/4/2024 88 9/4/2024 89  NUMERICAL PROBLEM 2 Calculate the reverse saturation current of a diode if the current at 0.2V forward bias is 0.1mA at a temperature of 25°C and the ideality factor is 1.5. a) 5.5x 10-9 A b) 5.5x 10-8 A c) 5.5x 10-7 A d) 5.6x 10-10 A 9/4/2024 90 9/4/2024 91  NUMERICAL PROBLEM 3 Find the applied voltage on a forward biased diode if the current is 1mA and reverse saturation current is 10-10. Temperature is 25°C and takes ideality factor as 1.5. a) 0.658V b) 0.726V c) 0.526V d) 0.618V 9/4/2024 92 9/4/2024 93  NUMERICAL PROBLEM 4 What will be the current I in the circuit diagram below. Take terminal voltage of diode as 0.7V and I0as 10-12A. a) 2.4mA b) 0.9mA c) 1mA d) 4mA 9/4/2024 94 9/4/2024 95 9/4/2024 96