A Research Assignment On Diode
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This document discusses diodes and provides details on their history, formation, biasing, characteristics, purposes, and types. It begins with defining a diode as a two-terminal electronic component that only allows current to flow in one direction. The history of diodes is then discussed from early thermionic diodes to the discovery of crystal semiconductor diodes. Diodes are formed from a P-N junction between a P-type and N-type semiconductor material. Biasing conditions of forward and reverse bias are described. The document concludes by outlining various diode types including small signal diodes, Zener diodes, LEDs, Schottky diodes, and more.
A Research Assignment On Diode
- 1. REPUBLIC OF THE PHILIPPINES TECHNOLOGICAL UNIVERSITY OF THE PHILIPPINES – CAVITE DEPARTMENT OF ENGINEERING SCIENCES C.Q.T. AVENUE, BRGY. SALAWAG, DASMARIAS CITY, CAVITE ASSIGNMENT NO. 1 RESEARCH: DIODES CURA, PATRICK ADRIAN SAURIN BSME – 2A ENGR. YVES INFANTA GONZALES JANUARY 30, 2020
- 2. TABLE OF CONTENT Page TITLE PAGE………………………………………………………………………………………………………….…….i TABLE OF CONTENTS…………………………………………………………………………………………….….ii TABLE OF FIGURES……………………………………………………………………………………………………iii STATEMENT OF THE PROBLEM…………………………………………………………………….…..……..iv RESEARCH CONTENT…………………………………………………………………………………………………1 1. DIODE……………………………………………………………………………………………..…………1 1.2. HISTORY………………………………………………………………………..…………..1 2. FORMATION OF DIODE………………………………………………………………………………2 3. BIASING OF DIODE……………………………………………………………………………………2 3.1. FORWARD BIAS………………………………………………………………….……..2 3.1.1. CIRCUITS UNDER FORWARD BIAS…………………………....3 3.2. REVERSE BIAS…………………………………………………………………..…….…3 3.1.1. CIRCUITS UNDER REVERSE BIAS……………………………...3 4. CHARACTERISTICS OF DIODE……………………………………………………………….…4 5. PURPOSE OF DIODE……………………………………………………………………………….…4 6. TYPES OF DIODE…………………………………………………………………………………….…4 6.1. SMALL SIGNAL DIODE…………………………………………………………….…4 6.2. ZENER DIODE…………………………………………………………………………….5 6.3. LIGHT EMITTING DIODE (LED)……………………………………………….…5 6.4. SCHOTTKY DIODE……………………………………………………………………..5 6.5. SHOCKLEY DIODE…………………….………………………………………….…….6 6.6. CONSTANT CURRENT DIODE………………………….………………………...6 6.7. STEP RECOVERY DIODE………………………….........…………..…….…….6 6.8. TUNNEL DIODE………………………………………………………….……….………7 6.9. VARACTOR DIODE………………………………………………….……….………..7 REFERENCES…………………………………………………………………………….......………….……………8
- 3. TABLE OF FIGURES Page FIGURE 1……………………………………………………………………………………………………….……….1 FIGURE 2………….…………………………………………………………………………………………….………1 FIGURE 3.………………………………………………………………………………………….……..……………2 FIGURE 4..……………………………………………………………………………………………….….…………3 FIGURE 5…………..……………………………………………………………………………………………………3 FIGURE 6…………..……………………………………………………………………………………………………4 FIGURE 7………….….…………………………………………………………………………………………………5 FIGURE 8..………………………………………………………………………………..……………………………5 FIGURE 9…………..……………………………………………………………………………………………………5 FIGURE 10………………………………………………………………………………………………………………6 FIGURE 11………………..……………………………………………………………………………………………6 FIGURE 12………..……………………………………………………………………………………………………6 FIGURE 13…….….……………………………………………………………………………………………………7 FIGURE 14………..……………………………………………………………………………………………………7 FIGURE 15………..……………………………………………………………………………………………………7
- 4. STATEMENT OF THE PROBLEM The research assignment aims to answer and elaborate the following questions regarding the topic about diodes, which may focus on: 1. What is the definition of diode? 2. Who are the proponents of diode? 3. How does diode being formed? 4. What are the characteristic of diode? 5. What is the purpose of diode? 6. What are the different types of diode?
- 5. 1 RESEARCH CONTENT 1. Diode In the field of electronics, a diode is a two-terminal electronic component that conducts electric current in only one direction. This term is usually referring to a semiconductor diode (the most common type nowadays) which is a crystal of semiconductor connected to two electrical terminals, a P-N junction. Further discussions are made after discoursing briefly the history of diode. An ideal diode will have zero resistance in one direction, and infinite resistance in the reverse direction. Figure 1 shows the symbol of diode in circuits. Figure 1. Symbol of Diode Although in the real world, diodes cannot achieve zero or infinite resistance. Instead, a diode will have negligible resistance in one direction (to allow current flow), and a very high resistance in the reverse direction (to prevent current flow). A diode is effectively like a valve for an electrical circuit. 1.2. History Thermionic diode (vacuum tubes, tubes, or valves) and solid state diodes were also developed parallel to the crystal semiconductor diode (a quite popular diode that time). The basic principle of operation of thermionic diodes was discovered by Frederic Guthrie in 1873. Afterwards, Thomas Edison on February 13, 1880 solely rediscover the principle during the time when he was carrying out research on why filaments of carbon-filament light bulb always burn at the positive connected end. Thomas later on patented a circuit where his modified light bulb more or less replaced the resistor in a DC voltmeter. It was called “Edison Effect”. Figure 2. The Edison Effect
- 6. 2 Then, John Ambrose Fleming, a former employee of Edison realized that the Edison effect could be used as a precision radio detector. Fleming patented the first true thermionic diode in Britain on November 16, 1904 (followed by U.S. Patent 803,684 in November 1905). Later on the principle of operation of crystal diodes was discovered in 1874 by the German scientist Karl Ferdinand Braun. Braun patented the crystal rectifier in 1899. Braun’s discovery was further developed by Jagdish Chandra Bose into a useful device for radio detection. In 1919, William Henry Eccles coined the term diode from the Greek roots dia, meaning “through”, and ode, meaning “path”. 2. Formation of Diode If a P-type and an N-type material are brought close to each other, both of them join to form a junction, as shown in the figure 3 below. Figure 3. P-Type and N-Type Material A P-type material has holes as the majority carriers and an N-type material has electrons as the majority carriers. As opposite charges attract, few holes in P-type tend to go to n-side, whereas few electrons in N-type tend to go to P- side. As this region acts as a barrier between P and N type materials, this is also called as Barrier junction. This has another name called as Depletion region meaning it depletes both the regions. There occurs a potential difference VD due to the formation of ions, across the junction called as Potential Barrier as it prevents further movement of holes and electrons through the junction. 3. Biasing of Diode When a diode or any two-terminal component is connected in a circuit, it has two biased conditions with the given supply. They are Forward biased condition and Reverse biased condition. 3.1. Forward Bias When a diode is connected in a circuit, with its anode to the positive terminal and cathode to the negative terminal of the supply, then such a connection is said to be forward biased condition.
- 7. 3 Figure 4. Forward Bias Connection This kind of connection makes the circuit more and more forward biased and helps in more conduction. A diode conducts well in forward biased condition. Figure 4 illustrate the condition of forward bias. 3.1.1. Circuits under Forward Bias With the repulsive force provided by positive terminal to holes and by negative terminal to electrons, the recombination takes place in the junction. The supply voltage should be such high that it forces the movement of electrons and holes through the barrier and to cross it to provide forward current. 3.2. Reverse Bias When a diode is connected in a circuit, with its anode to the negative terminal and cathode to the positive terminal of the supply, then such a connection is said to be Reverse biased condition. Figure 5. Reverse Bias Connection This kind of connection makes the circuit more and more reverse biased and helps in minimizing and preventing the conduction. A diode cannot conduct in reverse biased condition. Figure 5 shows the connection in reverse bias. 3.2.1. Circuits under Reverse Bias When anode and cathode are connected to negative and positive terminals respectively, the electrons are attracted towards the positive terminal and holes are attracted towards the negative terminal. Hence both will be away from the potential barrier increasing the junction resistance and preventing any electron to cross the junction.
- 8. 4 4. Characteristics of Diode A Practical circuit arrangement for a PN junction diode is as shown in Figure 6. Figure 6. Practical Diode Circuit During the operation, when the diode is in forward biased condition, at some particular voltage, the potential barrier gets eliminated. Such a voltage is called as Cut-off Voltage or Knee Voltage. If the forward voltage exceeds beyond the limit, the forward current rises up exponentially and if this is done further, the device is damaged due to overheating. During the reverse bias, current produced through minority carriers exist known as “Reverse current”. As the reverse voltage increases, this reverse current increases and it suddenly breaks down at a point, resulting in the permanent destruction of the junction. 5. Purpose of Diode A diode is used to block the electric current flow in one direction, i.e. in forward direction and to block in reverse direction. This principle of diode makes it work as a Rectifier. For a circuit to allow the current flow in one direction but to stop in the other direction, the rectifier diode is the best choice. Thus the output will be DC removing the AC components. The circuits such as half wave and full wave rectifiers are made using diodes, which can be studied in Electronic Circuits tutorials. A diode is also used as a Switch. It helps a faster ON and OFF for the output that should occur in a quick rate. 6. Types of Diode Different types of diodes have different voltage requirements. The following diodes are listed below. 6.1. Small Signal Diode The appearance of signal diode is very small when compared with the power diode. To indicate the cathode terminal one edge is marked with black or red in color. For the applications at high frequencies the performance of the small signal diode is very effective.
- 9. 5 With respect to the functional frequencies of the signal diode the carrying capacity of the current and power are very low which are maximum nearly at 150mA and 500mW. Figure 7. Small Signal Diode 6.2. Zener Diode It is a passive element works under the principle of zener breakdown. First produced by Clarence zener in 1934.It is similar to normal diode in forward direction, it also allows current in reverse direction when the applied voltage reaches the breakdown voltage. It is designed to prevent the other semiconductor devices from momentary voltage pulses. It acts as voltage regulator. Figure 8. Zener Diode (Example and Symbol) 6.3. Light Emitting Diode (LED) Earlier they used in inductor lamps but now in recent applications they are using in environmental and task handling. Mostly used in applications like aviation lighting, traffic signals, camera flashes. These diodes convert the electrical energy in to light energy. First production started in 1968. It undergoes electroluminescence process in which holes and electrons are recombined to produce energy in the form of light in forward bias condition. Figure 9. 5mm Green LED for Electronic Circuit 6.4. Schottky Diode In this type of diode the junction is formed by contacting the semiconductor material with metal. Due to this the forward voltage drop is decreased to min. The semiconductor material is N-type silicon which acts as an anode and the metal acts as a cathode whose materials are chromium, platinum, tungsten etc. Due to the metal junction these diodes have high current conducting capability thus the switching time reduces. So, Schottky has greater use in switching applications. Mainly because of the metal- semiconductor junction the voltage drop is low which in turn increase the diode performance and reduces power loss. So, these are used in high frequency rectifier applications.
- 10. 6 Figure 10. Schottky Diode Symbol 6.5. Shockley Diode It was the invention of first semiconductor devices it has four layers. It is also called as PNPN diode. It is equal to a thyristor without a gate terminal which means the gate terminal is disconnected. As there is no trigger inputs the only way the diode can conduct is by providing forward voltage. It stays on one’s it turned “ON” and stays off one’s it turned “OFF”. The diode has two operating states conducting and non-conducting. In non-conducting state the diode conducts with less voltage. Figure 11. Shockley Diode Symbol 6.6. Constant Current Diode It is also known as current-regulating diode or constant current diode or current-limiting diode or diode-connected transistor. The function of the diode is regulating the voltage at a particular current. It functions as a two terminal current limiter. In this JFET acts as current limiter to achieve high output impedance. The constant current diode symbol is shown below. Figure 12. Constant Current Diode Symbol 6.7. Step Recovery Diode It is also called as snap-off diode or charge-storage diode. These are the special type of diodes which stores the charge from positive pulse and uses in the negative pulse of the sinusoidal signals. The rise time of the current pulse is equal to the snap time. Due to this phenomenon it has speed recovery pulses.
- 11. 7 The applications of these diodes are in higher order multipliers and in pulse shaper circuits. The cut-off frequency of these diodes is very high which are nearly at Giga hertz order. Figure 13. Step Recovery Diode Symbol 6.8. Tunnel Diode It is used as high speed switch, of order nano-seconds. Due to tunneling effect it has very fast operation in microwave frequency region. It is a two terminal device in which concentration of dopants is too high. The transient response is being limited by junction capacitance plus stray wiring capacitance. Mostly used in microwave oscillators and amplifiers. It acts as most negative conductance device. Tunnel diodes can be tuned in both mechanically and electrically. The symbol of tunnel diode is as shown below. Figure 14. Tunnel Diode Symbol 6.9. Varactor Diode These are also known as Varicap diodes. It acts like the variable capacitor. Operations are performed mainly at reverse bias state only. These diodes are very famous due to its capability of changing the capacitance ranges within the circuit in the presence of constant voltage flow. They can able to vary capacitance up to high values. In varactor diode by changing the reverse bias voltage we can decrease or increase the depletion layer. These diodes have many applications as voltage controlled oscillator for cell phones, satellite pre-filters etc. The symbol of varactor diode is given below. Figure 15. Varactor Diode (Symbol and Example)
- 12. 8 REFERENCES Blom, P. W. M., Wolf, R. M., Cillessen, J. F. M., & Krijn, M. P. C. M. (1994). Ferroelectric schottky diode. Physical Review Letters, 73(15), 2107. Electrical4U (2020, January 4). Diode: Definition, Symbol and Types of Diodes. Retrieved from https://learn.sparkfun.com/tutorials /diodes/all History of Diode. (2016). Retrieved from http://www.juliantrubin.com/encyclopedia/electronics/diode.html Tutorials Point (2019). Basic Electronics – Junction Diode