Diodes

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  Microelectronics Engineering

  • (Author)
  • 2014(Publication Date)
  • Research World

    (Publisher)

  ________________________ WORLD TECHNOLOGIES ________________________ Chapter-7 Diode Figure 1: Closeup of a diode, showing the square shaped semiconductor crystal (black object on left) . ________________________ WORLD TECHNOLOGIES ________________________ Figure 2: Various semiconductor Diodes. Bottom: A bridge rectifier. In most Diodes, a white or black painted band identifies the cathode terminal, that is, the terminal which conventional current flows out of when the diode is conducting. ________________________ WORLD TECHNOLOGIES ________________________ Figure 3: Structure of a vacuum tube diode. The filament may be bare, or more commonly (as shown here), embedded within and insulated from an enclosing cathode In electronics, a diode is a two-terminal electronic component that conducts electric current in only one direction. The term usually refers to a semiconductor diode , the most common type today. This is a crystalline piece of semiconductor material connected to two electrical terminals. A vacuum tube diode (now little used except in some high-power technologies) is a vacuum tube with two electrodes: a plate and a cathode. The most common function of a diode is to allow an electric current to pass in one direction (called the diode's forward direction) while blocking current in the opposite direction (the reverse direction). Thus, the diode can be thought of as an electronic version of a check valve. This unidirectional behavior is called rectification, and is used ________________________ WORLD TECHNOLOGIES ________________________ to convert alternating current to direct current, and to extract modulation from radio signals in radio receivers. However, Diodes can have more complicated behavior than this simple on-off action. This is due to their complex non-linear electrical characteristics, which can be tailored by varying the construction of their P-N junction. These are exploited in special purpose Diodes that perform many different functions.

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  Foundations of Wireless and Electronics

  • M. G. Scroggie, S. W. Amos(Authors)
  • 2013(Publication Date)
  • Newnes

    (Publisher)

  CHAPTER 9 Diodes 9.1 Electronic Devices We now have all the essential basic principles of circuits, and it is time to strike out along a new line—electronics. Although all the electric currents we have been discussing in the last seven chapters consisted of electrons in motion there has been no real need to consider them as such. It would have been just about as easy to deal with the subject using one of the theories of the electric current in vogue before electrons were discovered. But now we are going to study electronic devices, which could not be satisfactorily explained without reference to electrons. It is these devices that are responsible for the rapid and multifarious developments included under the broad name of electronics. There are two main divisions of electronic devices: those in which the currents pass through vacuum or gas, and those in which they pass through semiconducting solids. The first includes those called valves in Britain and tubes in America, and the second includes transistors. Although some simple semiconductor devices were used, without knowing how they worked, for several decades before 1948, it was not until that year, when the transistor was invented as a result of research into the electronic nature of semiconductors, that they began to overtake thermionic valves (as they are named more fully), which are reckoned to have started in 1904. Electronic devices can be, and often are, classified according to the number of their electrodes. An electrode is not very easy to define precisely, but roughly it is any part of the device where a current leaves or enters or by means of which it is electrically controlled. Often each electrode has a terminal or wire by which connection is made to a circuit, but sometimes electrodes are connected together inside the device. 9.2 Diodes The least number of electrodes is two, and devices so constituted are called Diodes.

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  Engineering Circuit Analysis

  • J. David Irwin, R. Mark Nelms(Authors)
  • 2022(Publication Date)
  • Wiley

    (Publisher)

  C H A P T E R 16 16 Diodes The traffic light appeared early in the twentieth century. Incandescent bulbs were the primary source of illumination in traffic lights until the end of the twentieth century when traffic lights utilizing light-emitting Diodes (LEDs) were developed. LEDs are semiconductor devices that emit light when an electrical current is passed through them. Where a single incandescent bulb was used for each color in the light, each color in an LED traffic light is realized with an array of LEDs. In comparison to traffic lights employing incandescent bulbs, LED traffic lights have the following advantages: (1) they last longer because they do not have a filament to burn out, (2) they are brighter, and (3) they are more energy efficient. As a result, many cities are replacing older traffic lights with the newer LED-based traffic lights. Diodes are semiconductor devices employed in a variety of electrical circuits. They can be thought of as an electrical check valve—current can only flow through a diode in one direction. Diodes are utilized in a wide range of applications such as rectifiers, clamping circuits, and voltage regulators. Because of their widespread use, we will develop a basic understanding of the diode and learn how to analyze circuits containing Diodes in this chapter. 16.1 ❯ Introduction In this chapter we briefly introduce an electronic element that is widely used in circuits—the diode. Our discussion of the diode focuses on the construction of the device and four tech- niques that are used for modeling this element. The models are then used in circuit examples. Materials can generally be classified as conductors, insulators, or semiconductors. This distinction is based on the resistivity of the material measured in Ω-m. For example, copper wire has a resistivity of 1.72 × 10 −8 Ω-m at room temperature. The resistivity of hard rubber is on the order of 10 13 Ω-m, which places it in the category of an insulator.

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  Physical Properties of Materials For Engineers

  Volume 3

  • Daniel D. Pollock, Pollock(Authors)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  11.9 SEMICONDUCTOR DIODE DEVICES

  The devices discussed in the following sections have been included as being representative of some of the more commonly used Diodes. The intent is to demonstrate many of the more important physical mechanisms involved, rather than to provide a catalogue of devices.

  An important class of semiconductor Diodes is based upon single p-n junctions. The readily controlled charge carriers and electric fields in the depletion zones in the neighborhood of junctions make these devices possible (Section 11.6). The variations in the behaviors of the carriers and the internal electric fields when influenced by voltages, radiation, and other external effects determine the properties, type, and applications of the devices. Since the junctions are small, and the reactions take place near them, such devices can be, and are, made to be very small.

  The graphs are intended to show functional relationships, rather than actual values because of the variations in the properties of devices made by different sources. 11.9.1. Semiconductor Diode Rectifiers

  The polarity of the power supply is important in many electronic circuits. Power of the wrong sign can incapacitate many devices. Protection against this event may be obtained by the use of two oppositely oriented rectifiers in parallel between the supply and the circuit. Current of the wrong sign will be blocked by one of the rectifiers (negatively biased) and the circuit will be protected.

  In a comparable way, excessive voltage (overvoltage) can be eliminated by means of two oppositely oriented rectifiers in series between the input and the circuit. These limit the input voltage to the desired value without entering into the circuit.

  Two oppositely oriented rectifiers in parallel with each other, and connected in parallel with a suitable resistor across the terminals of a circuit, can provide protection against excessive current. In such an event, the rectifiers limit the excess current and allow only the desired amount of current to enter the circuit.

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  Principles of Analog Electronics

  • Giovanni Saggio(Author)
  • 2014(Publication Date)
  • CRC Press

    (Publisher)

  FIGURE 8.22 Traffic sign: one way directional arrow. Principles of Analog Electronics 274 There are several types of Diodes, differing in geometric scaling, doping level, and electrodes. But emphasizing different physical aspects, their v -i function can be changed accordingly. As a consequence, there are Diodes with electrical behav-ior that differs from the standard design. We refer to avalanche Diodes , Esaki or tunnel Diodes , thermal Diodes , photoDiodes , point-contact Diodes , PIN Diodes , Schottky Diodes , super barrier Diodes , step-recovery Diodes , varicaps or varac-tor Diodes , Peltier Diodes , gun Diodes , IMPATT Diodes , and so on. In the follow-ing, we will treat two of the most important ones: the Zener diode (Section 8.5.4) and the LED (Section 8.5.6). Observation The diode has numerous applications in electronics. We’ll detail some of the most important in the following sections. But now, let’s consider that the diode protects any electronic equipment (a radio, a recorder, etc.). In the event that the power source (battery or mains electricity) is connected the wrong way round, the diode prevents the current from flowing, so avoiding damaging or even destroying electronic devices. FIGURE 8.23 Blood circulation in the heart. The directions are controlled by the cardiac valves. Semiconductor Components 275 Another example is in our cars: the alternator charges the battery when the engine is running, but when the engine stops, a diode prevents the battery from discharging through the alternator (Figure 8.24). 8.5.1 The Bias The resistance of the depletion region can be modified by adding a fixed electric field to the built-in one. This operation is termed biasing , that is, the application of an external DC voltage, typically by means of a battery, across the junction. The added electric field can be in the same or opposite direction as the built-in electric field, determining an increase or a decrease of the resistance of the depletion region.

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  Intuitive Analog Circuit Design

  • Marc Thompson(Author)
  • 2006(Publication Date)
  • Newnes

    (Publisher)

  43 CHAPTER 3 Review of Diode Physics and the Ideal (and Later, Nonideal) Diode Current Flow in Insulators, Good Conductors and Semiconductors In nature, from the point of view of the ease of producing current flow in a material, there are three broad classes of materials: insulators, conductors and semiconductors. Semiconductors and metals can support significant current flow but the charge movement mechanisms are dif-ferent in the two types of materials. How “good” an electrical conductor is can be quantified by material property electrical resistivity and/or its inverse, electrical conductivity. Electrical resistivity 2 is a measure of how well a given material conducts current. If there are lots of free charged carriers available, a material is deemed a good conductor. In This Chapter f The basics of bipolar devices are covered, including basic semiconductor physics, 1 the concepts of electron and hole flow in semiconductors, the differences between drift and diffusion flow, generation and recombination, and the effects of semiconductor doping on carrier concentrations. We finish with a discussion of the ideal diode, and illustrate how a diode can conduct forward current, but can also block reverse voltage. Detailed mathematical derivations are avoided wherever possible. However, enough mathematical detail is given so that the reader can discern the important scaling laws and functional dependencies of the ideal diode. At the end of the chapter we’ll discuss some of the factors that result in nonideal behavior in Diodes. We’ll conclude with a discussion of load lines, a useful method for solving for the operating point of circuits with nonlinear devices. The load-line technique will be useful in later chapters in analyzing transistors. 1 W e will not go into the quantum mechanics of semiconductors, which provides the rigorous analyses. The simpler models developed in this chapter hopefully will give insight into the basics of semiconductor operation.

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  Reeds Vol 7: Advanced Electrotechnology for Marine Engineers

  • Christopher Lavers, Edmund G.R. Kraal(Authors)
  • 2014(Publication Date)
  • Thomas Reed

    (Publisher)

  An amplifier using semiconductors rather than vacuum is in principle possible. William Shockley (1939)

  Semiconductors

  This chapter introduces the semiconductor diode , a device comparable in function to the thermionic diode in the electronic circuits as discussed in Chapter 10 . Semiconductor materials have properties allowing their use for many device applications in response to temperature, pressure, stress, light, magnetic and electric fields. As such they are used frequently as sensors and transducers. The term ‘semiconductor’ includes all solids whose electrical conductivity lies between that of metals and insulators. Germanium and silicon, and gallium arsenide are perhaps the most important semiconductor materials of current working device choice, but graphene, a substance made from pure carbon, with atoms arranged in a regular hexagonal pattern similar to graphite but only one atom thick, may provide novel new commercial devices in the near future. However, before investigating the electrical properties of current materials such as germanium and silicon, it is worth recalling the history of semiconductor development in electrical work. The electrical properties of semiconductor materials will then be examined, without which diode and transistor operation will not be understood.

  ‘Solid-state’ devices, as their name might suggest, are not vacuum devices like the thermionic valve, and it is their ability to control conductivity without the need for bulky yet delicate glass bulbs that make solid-state devices so attractive for most practical purposes.

  The rectifying properties of the diode had been grounded in the fundamental work of the late nineteenth century onwards also providing the advent of radio through the thermionic valve and the rectifying crystal. In 1833, Michael Faraday discovered that silver sulphide had a negative temperature coefficient of resistance. Austrian physicist Braun (1874) investigated the resistance properties of various contacts between metals and their oxides, using a wire as a point contact, and noted that resistance depended on the polarity of the applied voltage. He also observed the rectification effects of selenium. Point contact rectifiers were used for a considerable period, in fact they were used in the early days of wireless up to the 1920s. The rectifying crystal, a natural semiconductor diode, was later replaced by the valve which in time became the triode and used for detection, rectification and amplification. The crystal also became popular as a detector in the early days of broadcasting because of its cheapness and the device was often called the cats-whisker

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  Fundamental Electrical and Electronic Principles

  • Jo Verhaevert, Christopher R. Robertson(Authors)
  • 2024(Publication Date)
  • Routledge

    (Publisher)

  Chapter 6 Semiconductor Theory and Diodes

  DOI: 10.1201/9781003308294-6

  Learning Outcomes This chapter explains the behaviour of semiconductors and the way in which they are employed in Diodes. On completion of this chapter you should be able to:

  1. Understand the way in which conduction takes place in semiconductor materials.
  2. Understand how these materials are employed to form devices such as Diodes.
  3. Understand the action of a zener diode and perform basic calculations involving a simple regulator circuit.
  4. Understand the action of a LED and a solar cell and perform basic calculations on the use of it.

  6.1 Atomic Structure

  In Chapter 1 it was stated that an atom consists of a central nucleus containing positively charged protons, and neutrons, the latter being electrically neutral, surrounded by negatively charged electrons orbiting in layers or shells. Electrons in the inner orbits or shells have the least energy and are tightly bound into their orbits due to the electrostatic force of attraction between them and the nucleus. Electrons in the outermost shell experience a much weaker binding force, and are known as valence electrons.

  In conductors, like copper or silver, it is these valence electrons that can gain sufficient energy to break free from their parent atoms. They have a hard time keeping that electron and therefore copper and silver are good conductors: when these valence electrons transfer to another atom, they create a changing electric field. These ‘free’ electrons are available to drift through the material under the influence of an emf and hence are mobile charge carriers which produce current flow.

  The shells are identified by letters of the alphabet, beginning with the letter K for the innermost shell, L for the next and so on. Each shell represents a certain energy level, and each shell can contain only up to a certain maximum number of electrons. This maximum possible number of electrons contained in a given shell is governed by the relationship 2n2 , where n is the number of the shell. Thus the maximum number of electrons in the first four shells will be as shown in Table 6.1

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  Electricity and Electronics Fundamentals, Second Edition

  • Dale R. Patrick, Stephen W. Fardo(Authors)
  • 2020(Publication Date)
  • River Publishers

    (Publisher)

  This in turn would cause V Z and the load voltage to remain at 15 V. A decrease in supply voltage to 20 V would cause a reduc- tion in total current. The voltage drop across R S would now drop to only 5 V. The load voltage across the diode would continue to be 15 V. This means that the regulated output will remain at 15 V for a change in supply voltage from 20 to 30 V. Voltage regulation is an important func- tion of many electronic circuits today. LIGHT-EMITTING Diodes The light-emitting diode (LED) is another important diode device. It contains a P-N junction that emits light when passing forward current. A schematic symbol and typical package of the LED are shown in Figure 3-29(a) and (b). The lens of an LED (Figure 3-29(c)) is transparent and focuses on the P-N junction. When an LED is forward-biased, electrons cross the junction and combine with holes. This action causes electrons to fall out of conduction and return to the va- lence band. The energy possessed by each free electron is then released. Some of this appears as heat energy and the rest of it is given off as light energy. Special materials such as gallium arsenide (GaAs) and gallium phosphide (GaP) cause this to take place when used in a P-N junc- tion. These materials are purposely used because they emit visible light energy. Light-emitting Diodes are relatively small, ruggedly constructed, and have a very long life expectancy. They can be switched on and off very quickly. Construction techniques permit this type of device to be made in vari- ous shapes and patterns. A very common application is in numeric displays indicating the numbers 0 through 9. A representative LED seven-segment display is shown in Figure 3-30. By selecting different combinations of seg- ments, a desired number can be produced. Displays of this type are found in calculators, digital meters, clocks, and wristwatches. Figure 3-29. Light-emitting diode: (a) symbol; (b) crystal structure; (c) transparent lens.

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  Analog Electronic Circuit

  • Beijia Ning(Author)
  • 2018(Publication Date)
  • De Gruyter

    (Publisher)

  D is beyond the voltage drop across the Diodes. The defined direction of conventional current for the forward voltage region matches the arrowhead in the diode symbol.
• When in the reverse-biased condition, the direction of I S is against the symbolic direction of I D . Also, the reverse current rises quickly and soon reaches the saturation level. However, for a commonly-used diode, the actual reverse saturation current will normally be measurable as larger than that from the curve.
Fig. 2.4: Forward-bias condition of s semiconductor diode, (a) Internal carrier distribution under forward-bias condition, (b) Electrical symbols of forward-bias condition.
Fig. 2.5: Silicon semiconductor diode characteristics.