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electronics,science and technology based on and concerned with the controlled flow of electronselectron,
elementary particle carrying a unit charge of negative electricity. Ordinary electric current is the flow of electrons through a wire conductor (see electricity). The electron is one of the basic constituents of matter.
..... Click the link for more information. or other carriers of electric charge, especially in semiconductorsemiconductor,
solid material whose electrical conductivity at room temperature is between that of a conductor and that of an insulator (see conduction; insulation). At high temperatures its conductivity approaches that of a metal, and at low temperatures it acts as an insulator.
..... Click the link for more information. devices. It is one of the principal branches of electrical engineeringengineering,
profession devoted to designing, constructing, and operating the structures, machines, and other devices of industry and everyday life. Types of Engineering
The primary types of engineering are chemical, civil, electrical, industrial, and mechanical.
..... Click the link for more information. . The invention of the transistor, announced in 1948, and the subsequent development of integrated circuitsintegrated circuit
(IC), electronic circuit built on a semiconductor substrate, usually one of single-crystal silicon. The circuit, often called a chip, is packaged in a hermetically sealed case or a nonhermetic plastic capsule, with leads extending from it for input, output,
..... Click the link for more information. have brought about revolutionary changes in electronics, which was previously based on the technology of the electron tubeelectron tube,
device consisting of a sealed enclosure in which electrons flow between electrodes separated either by a vacuum (in a vacuum tube) or by an ionized gas at low pressure (in a gas tube).
..... Click the link for more information. . The miniaturization and savings in power brought about by these developments have allowed electronic circuits to be packaged more densely, making possible compact computers, advanced radar and navigation systems, and other devices that use very large numbers of components (see microelectronicsmicroelectronics,
branch of electronic technology devoted to the design and development of extremely small electronic devices that consume very little electric power. Although the term is sometimes used to describe discrete electronic components assembled in an extremely small
..... Click the link for more information. ). It has also brought to the consumer such items as smaller and more reliable radioradio,
transmission or reception of electromagnetic radiation in the radio frequency range. The term is commonly applied also to the equipment used, especially to the radio receiver.
..... Click the link for more information. and televisiontelevision,
transmission and reception of still or moving images by means of electrical signals, originally primarily by means of electromagnetic radiation using the techniques of radio, now also by fiber-optic and coaxial cables and other means.
..... Click the link for more information. receivers, advanced sound- and video-recording and reproducing systems, microwave ovensmicrowave oven,
device that uses microwaves to rapidly cook food. The microwaves cause water molecules in the food to vibrate, producing heat, which is distributed through the food by induction. A special electron tube called a magnetron produces the microwaves.
..... Click the link for more information. , cellular telephones, and powerful yet inexpensive personal computers. The consumer electronics industry—which began in 1920 when radio broadcasting started in the United States—accounts for annual sales of close to $50 billion in the United States alone. Because of advances in electronics manufacturing technology, the cost of electronic products often decreases even as quality and reliability increase. Power requirements are continually reduced, allowing greater portability.
the science that deals with the interaction of electrons and electromagnetic fields and with the methods of developing electronic devices and equipment, in which the interaction is used to convert electromagnetic energy for, primarily, the transmission, processing, and storage of information. The most typical conversions are the generation, amplification, and detection of electromagnetic oscillations at frequencies of up to 1012hertz (Hz), as well as at frequencies in the range from 1012 Hz to 1020 Hz, which includes infrared, visible, and ultraviolet radiation and X-rays. Conversion at such high frequencies is possible because of the exceptionally low response time of the electron, which is the smallest of all known charged particles. Electronics investigates the interactions of electrons both with the macro-fields in the working cavities of electronic devices and with the microfields in atoms, molecules, and crystal lattices.
Electronics is based on various branches of physics—electrodynamics, classical and quantum mechanics, optics, thermodynamics, and solid-state physics—and on such sciences as chemistry, metallurgy, and crystallography. Using the findings of these and other bodies of knowledge, electronics defines new tasks for other sciences, thereby stimulating their development. In addition, electronics creates devices and equipment that provide the sciences with new means and methods of investigation.
An important practical contribution of electronics is the development of devices that perform various functions in systems used for the conversion and transmission of information, in control systems, in computer apparatus, and in equipment for the energy industry. Electronics also formulates the scientific principles underlying the technology used in the manufacture of electronic devices and the technology that applies electronic and ionic processes and devices to various fields of science and engineering.
Electronics is playing a leading role in the scientific and technical revolution. The introduction of electronic devices in various areas of human activity contributes in large and often decisive measure to the resolution of complex scientific and technical problems, to an increase in the productivity of physical and mental labor, and to the improvement of economic indexes of production. The achievements of electronics have formed the basis of an industry that produces electronic equipment used in communications, automation, television, radar, computer technology, instrument-making, and industrial-process control systems, as well as illuminating-engineering, infrared, and X-ray equipment.
Historical survey. Electronics as a science originated in the early 20th century, after a series of important advances had been recorded. Between 1856 and 1873, the principles of electrodynamics were formulated. Thermionic emission was investigated between 1882 and 1901, photoelectric emission between 1887 and 1905, and X rays between 1895 and 1897. J. J. Thompson discovered the electron in 1897, and between 1892 and 1909 the classical electron theory took shape.
The development of electronics began with the invention of the diode tube by J. A. Fleming in 1904 and the three-electrode tube, or triode, by L. De Forest in 1906. In 1913, the German engineer A. Meissner used a triode to generate electric oscillations. Between 1919 and 1925, M. A. Bonch-Bruevich developed powerful water-cooled vacuum-tube generators for radio transmitters used in long-range radio communication and broadcasting.
An experimental prototype of a phototube was constructed by A. G. Stoletov in 1888, and industrial models were prepared by the German scientists J. Elster and H. Geitel in 1910. P. V. Timofeev developed a single-stage multiplier phototube in 1928, and L. A. Kubetskii a multistage multiplier phototube in 1930.
The invention of the phototube made sound motion pictures possible. In addition, such television camera tubes as the vidicon, the iconoscope, the image iconoscope, and the image orthicon were developed on the basis of the phototube. A design for the vidicon was proposed by A. A. Chernyshev in 1925. S. I. Kataev and V. K. Zworykin, working independently of each other, developed iconoscopes in 1931 and 1932, and P. V. Timofeev and P. V. Shmakov invented the image iconoscope in 1933. The image orthicon was first described in 1946 by the American scientists A. Rose, P. Weimer, and H. Law. A two-sided target for such a tube, however, was proposed in 1939 by the Soviet scientist G. V. Braude.
A framework for the development of radar in the centimeter range was provided by the invention of the multiresonator magnetron in 1936–37 by N. F. Alekseev and D. E. Maliarov, who were working under M. A. Bonch-Bruevich. The development of a reflex klystron in 1940 by N. D. Deviatkov and co-workers and, independently, by the Soviet engineer V. F. Kovalenko also contributed to this framework. The drift-tube klystron and the traveling-wave tube, which was developed in 1943 by the American scientist R. Kompfner, made possible development of radio relay communication systems and particle accelerators and contributed to the creation of space communication systems. The concept of the drift-tube klystron was proposed in 1932 by D. A. Rozhanskii. The device was developed in 1935 by the Soviet physicist A. N. Arsen’eva and the German physicist O. Heil and constructed in 1938 by the American physicists R. and S. Varian and others.
Gas-discharge, or ion, devices were developed and improved concurrently with vacuum-tube devices. Such gas-discharge devices included mercury-arc rectifiers, which are used primarily to convert alternating current to direct current in high-power industrial installations; thyratrons, which shape powerful pulses of electric current in pulse-forming devices; and gas-discharge light sources.
Semiconductor electronics began with the use of crystalline semiconductors as detectors in radio receivers between 1900 and 1905. Its development continued with the invention of copper oxide and selenium current rectifiers and photocells between 1920 and 1926 and with O. V. Losev’s invention of the oscillating crystal receiver in 1922. W. Shockley, W. Brattain, and J. Bardeen’s invention of the transistor, in 1948, marked the beginning of an era of expansion in the field.
The development of the planar process for fabricating semiconductor structures and of methods of integrating a large number of microelements, such as transistors, diodes, capacitors, and resistors, on a single-crystal semiconductor wafer led to a new trend in electronics—microelectronics (see alsoINTEGRATED ELECTRONICS). The principal efforts in integrated electronics have been aimed at the development of integrated circuits—microminiature electronic devices, such as amplifiers, converters, central processing units, and memories. Integrated circuits consists of hundreds or even thousands of electronic devices placed on a single semiconductor crystal that has an area of several square millimeters. Microelectronics has provided new opportunities for the solution of such problems associated with the growth of contemporary social production as the automation of industrial process control, the processing of information, and the improvement of computer technology.
The invention of the maser—a quantum electronics device developed in 1955 by N. G. Basov and A. M. Prokhorov and, independently, by C. Townes—revealed the unique potential of electronics that is associated with use of the powerful coherent light of lasers and with the synthesis of extremely precise quantum frequency standards.
Soviet scientists have made a large contribution to the development of electronics. Fundamental investigations in the physics and technology of electronic devices have been carried out by many researchers, including M. A. Bonch-Bruevich, L. I. Mandel’shtam, N. D. Papaleksi, S. A. Vekshinskii, A. A. Chernyshev, and M. M. Bogoslovskii. B. A. Vvedenskii, V. D. Kalmykov, A. L. Mints, A. A. Raspletin, and M. V. Shuleikin are among those who have studied problems associated with the excitation and conversion of electric oscillations, with the emission, propagation, and reception of radio waves, and with the interaction of radio waves and current carriers in a vacuum, in gases, and in solids. A. F. Ioffe carried out original research in the physics of semiconductors, S. I. Vavilov in luminescence and other areas of physical optics, and I. E. Tamm in the quantum theory of the scattering of light, in radiation theory, and in the theory of the photoeffect in metals.
Fields, principal branches, and areas of application. Electronics comprises three fields of research: vacuum electronics, solid-state electronics, and quantum electronics. Each field is subdivided into a number of branches and a number of areas of application. A branch combines groups of like physiochemical phenomena and processes that are of fundamental importance to the development of many classes of electronic devices in a given area. An area of application encompasses not only the methods of designing and constructing electronic devices that are similar in operating principle or function but also the techniques used in the devices’ manufacture.
VACUUM ELECTRONICS. Vacuum electronics includes the following branches: (1) emission electronics, which encompasses thermionic emission, photoemission, secondary emission, and field emission, as well as problems of cathodes and antiemission coatings; (2) the formation and control of electron and ion fluxes; (3) the formation of electromagnetic fields with resonators, resonator systems, slow-wave circuits, and power input and output devices; (4) electronoluminescence, or cathodoluminescence; (5) the physics and technology of high vacuums, that is, the production, maintenance, and monitoring of high vacuums; (6) thermal processes such as vaporization in a vacuum, deformation of parts under cyclic heating, surface breakdown of metals under pulsed heating, and heat discharge of equipment components; (7) surface phenomena associated with the formation of films on electrodes and insulators and of irregularities on electrode surfaces; (8) surface-treatment technology, which includes treatment with electron beams, ions, and lasers; and (9) gas media, a branch that includes aspects of the production and maintenance of optimal gas composition and pressure in gas discharge devices.
The principal areas of application of vacuum electronics encompass aspects of the development of various electron-tube devices. These devices include such vacuum tubes as triodes, tetrodes, and pentodes; such microwave tubes as magnetrons and klystrons; such electron-beam devices as picture tubes and oscillograph tubes; such photoelectric devices as phototubes and photomultipliers; X-ray tubes; and such gas-discharge devices as high-power rectifiers, light sources, and indicators.
SOLID-STATE ELECTRONICS. The branches and areas of application of solid-state electronics are associated primarily with semiconductor electronics. The principal branches of semiconductor electronics are the following: (1) the study of the properties of semiconductor materials and the effects of impurities on those properties; (2) the creation of areas of differing conductivity on a single crystal by means of epitaxy (see), diffusion, ion implantation, or irradiation of semiconductor structures; (3) the application of dielectric and metallic films on semiconductor materials and the development of the technology for fabricating films with the necessary properties and configurations; (4) the investigation of the physical and chemical processes that occur on semiconductor surfaces; and (5) the development of methods and equipment for producing and measuring microelements that are a few micrometers or less in size.
The basic areas of application of semiconductor electronics are associated with the development and manufacture of various types of semiconductor devices. Such devices include semiconductor diodes (rectifier, mixer, parametric, and avalanche diodes), amplifier and oscillator diodes (tunnel, avalanche transit time, and Gunn diodes), transistors (bipolar and unipolar), thyristors, optoelectronic devices (light-emitting diodes, photo-diodes, phototransistors, optrons, and light-emitting-diode and photodiode matrices), and integrated circuits.
The areas of application of solid-state electronics also include dielectric electronics, magnetoelectronics, acoustoelectronics, piezoelectronics, cryoelectronics, and the development and manufacture of resistors.
Dielectric electronics deals with the electronic processes that occur in dielectrics—particularly in thin dielectric films—and the use of such processes in, for example, the development of dielectric diodes and capacitors. Magnetoelectronics makes use of the magnetic properties of matter to control the flow of electromagnetic energy by means of ferrite isolators, circulators, and phase shifters and to develop memories, including those based on ferromagnetic domains.
Acoustoelectronics and piezoelectronics deal with the propagation of acoustic surface and body waves, the variable electric fields that such waves generate in crystalline materials, and the interaction of the fields with electrons in devices with a piezoelectric semiconductor structure, such as quartz frequency stabilizers, piezoelectric filters, ultrasonic delay lines, and acoustoelectronic amplifiers. Cryoelectronics, in which the changes brought about in the properties of solids by extremely low temperatures are studied, involves the construction of low-noise microwave amplifiers and oscillators and ultrahigh-speed computers and memories, as well as the design and manufacture of resistors.
QUANTUM ELECTRONICS. The most important application of quantum electronics is the development of lasers and masers. Quantum electronics devices serve as the basis of instruments used for the accurate measurement of distances (range finders), quantum frequency standards, quantum gyroscopes, optical-frequency multichannel communication systems, long-range space communication systems, and radio astronomy. The powerful action of laser radiation on matter is made use of in industry. Lasers also find application in biology and medicine.
Electronics is in a stage of intense development. New fields of electronics are evolving, and new areas of application in the current fields are being found.
The technology of electronic devices. The design and manufacture of electronic devices are based on the use of physicochemical processes and a combination of various properties of materials. It is necessary, therefore, to understand thoroughly the processes used and their effects on the properties of the devices and to be able to control the processes with precision.
The great importance of physicochemical research and of the development of the scientific bases of engineering in electronics stems from the dependence of the properties of electronic devices on the presence of doping agents and substances adsorbed on the surfaces of a device’s working elements, as well as the dependence of the properties on gas composition and the degree of rarefaction of the medium surrounding the elements. It is also due to the dependence of the reliability and service life of electronic devices on the degree of stability of the raw materials used and on the controllability of the fabrication technology.
Technological advances often stimulate the development of new areas of application in electronics. Engineering features common to all areas of application of electronics are the requirements—exceptionally high in comparison with other branches of technology—that the electronics industry imposes on the properties of the raw materials used, on the degree of protection provided for the workpieces during production, and on the geometric precision of the fabrication of electronic devices.
Fulfillment of the first of these requirements makes possible the synthesis of ultrapure materials with a structure that has a high degree of perfection and with predetermined physicochemical properties. The development of such materials—which include special composites of single crystals, ceramics, and glasses—and the study of their properties constitute the subject of a special scientific and engineering discipline called electronic materials science.
One of the most acute engineering problems associated with the second requirement is dust control in the gaseous medium in which the most critical fabrication processes take place. In many cases, no more than three dust particles of less than 1 micrometer in diameter are acceptable per cubic meter.
The requirements for geometric precision in the fabrication of electronic devices are exceedingly stringent. Often, the relative error in size cannot exceed 0.001 percent, and the dimensions and relative positions of the elements of integrated circuits must be accurate to hundredths of a micrometer. Such stringency dictates that new, more advanced methods of working with materials be developed, as well as new techniques and equipment for quality control.
Manufacturing processes in electronics require extensive use of the latest methods and technology, which include electron-beam, ultrasonic, and laser processing and welding; photolithography and electron-beam and X-ray lithography; electron-discharge machining; ion implantation; plasma chemistry; molecular epitaxy; electron microscopy; and techniques that employ vacuum devices with a residual gas pressure of as low as 10–13 mm Hg.
Apart from the general aims of increasing labor productivity, the automation of the production of electronic devices through the use of computers is made imperative by a degree of complexity in many manufacturing processes that requires the elimination of subjective human influence. These and other features of the manufacturing processes in electronics have necessitated the creation of a new area of application of machine building—electronic machine building.
Prospects for development. One of the primary problems facing electronics is the need to reduce the size and power consumption of computer and electronic control systems while increasing the amounts of information processed. This problem is being solved in a number of ways. Integrated circuits that have a switching time of as little as 10–11 sec are being developed, and the degree of integration is being increased so that as many as 1 million transistors can placed on a crystal 1–2 micrometers long. Optical-frequency communication devices, optoelectronic converters, and superconductors are being used in integrated circuits, and memories with capacities of several megabits are being designed for single semiconductor crystals. The problem is also being addressed by the use of laser and electron-beam switching and by the expansion of the functional capabilities of integrated circuits. For example, microcomputers, rather than simply microprocessors, are being placed on single semiconductor crystals. The changeover from the two-dimensional, or planar, technology of integrated circuits to three-dimensional, or bulk, technology and the use of a combination of the various properties of a solid in one device are also helping to solve the problem. The principles and techniques of stereoscopic television, which can convey more information than can conventional television, are being developed and implemented, and electronic devices operating in the millimeter and submillimeter regions are being fabricated for wide-band and, consequently, more efficient data transmission systems.
Electronic methods and equipment are used in biology in the study of cells and the structure and responses of living organisms and in medicine in diagnostics, therapy, and surgery. As electronics develops and the technology of the production of electronic devices improves, the range of application of electronics will expand in all areas of human life and activity, and the role of electronics in accelerating scientific and technical progress will grow.
A. I. SHOKIN
Technology involving the manipulation of voltages and electric currents through the use of various devices for the purpose of performing some useful action. This large field is generally divided into two primary areas, analog electronics and digital electronics.
Historically, analog electronics was used in large part because of the ease with which circuits could be implemented with analog devices. However, as signals have become more complex, and the ability to fabricate extremely complex digital circuits has increased, the disadvantages of analog electronics have increased in importance, while the importance of simplicity has declined.
In analog electronics, the signals to be manipulated take the form of continuous currents or voltages. The information in the signal is carried by the value of the current or voltage at a particular time t. Some examples of analog electronic signals are amplitude-modulated (AM) and frequency-modulated (FM) radio broadcast signals, thermocouple temperature data signals, and standard audio cassette recording signals. In each of these cases, analog electronic devices and circuits can be used to render the signals intelligible.
Commonly required manipulations include amplification, rectification, and conversion to a nonelectronic signal. Amplification is required when the strength of a signal of interest is not sufficient to perform the task that the signal is required to do. However, the amplification process suffers from the two primary disadvantages of analog electronics: (1) susceptibility to replication errors due to nonlinearities in the amplification process and (2) susceptibility to signal degradation due to the addition, during the amplification process, of noise originating from the analog devices composing the amplifier. These two disadvantages compete with the primary advantage of analog electronics, the ease of implementing any desired electronic signal manipulation. See Amplifier, Distortion (electronic circuits)
The advent of the transistor in the 1940s made it possible to design simple, inexpensive digital electronic circuits and initiated the explosive growth of digital electronics. Digital signals are represented by a finite set of states rather than a continuum, as is the case for the analog signal. Typically, a digital signal takes on the value 0 or 1; such a signal is called a binary signal. Because digital signals have only a finite set of states, they are amenable to error-correction techniques; this feature gives digital electronics its principal advantage over analog electronics. See Transistor
In common two-level digital electronics, signals are manipulated mathematically. These mathematical operations are known as boolean algebra. The operations permissible in boolean algebra are NOT, AND, OR, and XOR, plus various combinations of these elemental operations.
Electronic circuits are composed of various electronic devices, such as transistors, resistors, and capacitors. In circuits built from discrete components, the components are typically soldered together on a fiberglass board known as a printed circuit board. On one or more surfaces of the printed circuit board are layers of conductive material which has been patterned to form the interconnections between the different components in the circuit. In some cases, the circuits necessary for a particular application are far too complex to build from individual discrete components, and integrated-circuit technology must be employed. Integrated circuits are fabricated entirely from a single piece of semiconductor substrate. It is possible in some cases to put several million electronic devices inside the same integrated circuit. Many integrated circuits can be fabricated on a single wafer of silicon at one time, and at the end of the fabrication process the wafer is sawed into individual integrated circuits. These small pieces, or chips as they are popularly known, are then packaged appropriately for their intended application. See Capacitor, Integrated circuits, Printed circuit
The microprocessor is the most important integrated circuit to arise from the field of electronics. This circuit consists of a set of subcircuits that can perform the tasks necessary for computation and are the heart of modern computers. Microprocessors that understand large numbers of instructions are called complete instruction set computers (CISCs), and microprocessors that have only a very limited instruction set are called reduced instruction set computers (RISCs). See Digital computer
Other circuit designs have been standardized and reduced to integrated-circuit form as well. An example of this process is seen in the telephone modem. Modulation techniques have been standardized to permit the largest possible data-transfer rates in a given amount of bandwidth, and standardized modem chips are available for use in circuit design. See Modem
The memory chip is another important integrated electronic circuit. This circuit consists of a large array of memory cells composed of a transistor and some other circuitry. As the storage capacity of the memory chip has increased, significant miniaturization has taken place. See Circuit (electronics)