electronics

electronics

[ih-lek-tron-iks, ee-lek-]
electronics, science and technology based on and concerned with the controlled flow of electrons or other carriers of electric charge, especially in semiconductor devices. It is one of the principal branches of electrical engineering. The invention of the transistor, announced in 1948, and the subsequent development of integrated circuits have brought about revolutionary changes in electronics, which was previously based on the technology of the electron tube. 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 microelectronics). It has also brought to the consumer such items as smaller and more reliable radio and television receivers, advanced sound- and video-recording and reproducing systems, microwave ovens, 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.

Branch of engineering concerned with the practical applications of electricity in all its forms, including those of electronics. Electrical engineering deals with electric light and power systems and apparatuses; electronics engineering deals with wire and radio communication, the stored-program electronic computer, radar, and automatic control systems. The first practical application of electricity was the telegraph, in 1837. Electrical engineering emerged as a discipline in 1864 when James Clerk Maxwell summarized the basic laws of electricity in mathematical form and predicted that radiation of electromagnetic energy would occur in a form that later became known as radio waves. The need for electrical engineers was not felt until the invention of the telephone (1876) and the incandescent lamp (1878).

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Branch of physics that deals with the emission, behaviour, and effects of electrons and with electronic devices. The beginnings of electronics can be traced to experiments with electricity. In the 1880s Thomas Alva Edison and others observed the flow of current between elements in an evacuated glass tube. A two-electrode vacuum tube constructed by John A. Fleming (1849–1945) produced a useful output current. The Audion, invented by Lee De Forest (1907), was followed by further improvements. The invention of the transistor at Bell Labs (1947) initiated a progressive miniaturization of electronic components that by the mid 1980s resulted in high-density microprocessors, which in turn led to tremendous advances in computer technology and computer-based automated systems. Seealso semiconductor.

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Electronics refers to the flow of charge (moving electrons) through nonmetal conductors (mainly semiconductors), whereas electrical refers to the flow of charge through metal conductors. For example, flow of charge through silicon, which is not a metal, would come under electronics; whereas flow of charge through copper, which is a metal, would come under electrical. This distinction started around 1908 with the invention by Lee De Forest of the triode. Until 1950 this field was called "Radio technics" because its principal application was the design and theory of radio transmitters and receivers.

The study of new semiconductor devices and related technology is considered a branch of physics whereas the design and construction of electronic circuits to solve practical problems comes under electronics engineering. This article focuses on engineering aspects of electronics.

Electronic devices and components

An electronic component is any physical entity in an electronic system whose intention is to affect the electrons or their associated fields in a desired manner consistent with the intended function of the electronic system. Components are generally intended to be in mutual electromechanical contact, usually by being soldered to a printed circuit board (PCB), to create an electronic circuit with a particular function (for example an amplifier, radio receiver, or oscillator). Components may be packaged singly or in more complex groups as integrated circuits. Some common electronic components are capacitors, resistors, diodes, transistors etc.

Types of circuits

Analog circuits

Most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a continuous range of voltage as opposed to discrete levels as in digital circuits.

The number of different analog circuits so far devised is huge, especially because a 'circuit' can be defined as anything from a single component, to systems containing thousands of components.

Analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, operational amplifiers and oscillators.

Some analog circuitry these days may use digital or even microprocessor techniques to improve upon the basic performance of the circuit. This type of circuit is usually called "mixed signal." Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation. An example is the comparator which takes in a continuous range of voltage but puts out only one of two levels as in a digital circuit. Similarly, an overdriven transistor amplifier can take on the characteristics of a controlled switch having essentially two levels of output.

Digital circuits

Digital circuits are electric circuits based on a number of discrete voltage levels. Digital circuits are the most common physical representation of Boolean algebra and are the basis of all digital computers. To most engineers, the terms "digital circuit", "digital system" and "logic" are interchangeable in the context of digital circuits. In most cases the number of different states of a node is two, represented by two voltage levels labeled "Low"(0) and "High"(1). Often "Low" will be near zero volts and "High" will be at a higher level depending on the supply voltage in use.

Computers, electronic clocks, and programmable logic controllers (used to control industrial processes) are constructed of digital circuits. Digital Signal Processors are another example.

Building-blocks:

Highly integrated devices:

Heat dissipation and thermal management

Heat generated by electronic circuitry must be dissipated to prevent immediate failure and improve long term reliability. Techniques for heat dissipation can include heatsinks and fans for air cooling, and other forms of computer cooling such as water cooling. These techniques use convection, conduction, & radiation of heat energy.

Noise

Noise is associated with all electronic circuits. Noise is defined as unwanted disturbances superposed on a useful signal that tend to obscure its information content. Noise is not the same as signal distortion caused by a circuit.

Electronics theory

Mathematical methods are integral to the study of electronics. To become proficient in electronics it is also necessary to become proficient in the mathematics of circuit analysis.

Circuit analysis is the study of methods of solving generally linear systems for unknown variables such as the voltage at a certain node or the current though a certain branch of a network. A common analytical tool for this is the SPICE circuit simulator.

Also important to electronics is the study and understanding of electromagnetic field theory.

Computer aided design (CAD)

Today's electronics engineers have the ability to design circuits using premanufactured building blocks such as power supplies, semiconductors (such as transistors), and integrated circuits. Electronic design automation software programs include schematic capture programs and printed circuit board design programs. Popular names in the EDA software world are NI Multisim, Cadence (ORCAD), Ea"gle PCB and Schematic, Mentor (PADS PCB and LOGIC Schematic), Altium (Protel), LabCentre Electronics (Proteus) and many others."

Construction methods

Many different methods of connecting components have been used over the years. For instance, early electronics often used point to point wiring with components attached to wooden breadboards to construct circuits. Cordwood construction and wire wraps were other methods used. Most modern day electronics now use printed circuit boards (made of FR4), and highly integrated circuits. Health and environmental concerns associated with electronics assembly have gained increased attention in recent years, especially for products destined to the European Union, with its Restriction of Hazardous Substances Directive (RoHS) and Waste Electrical and Electronic Equipment Directive (WEEE), which went into force in July 2006.

Electronics industry

Branch pages

See also

References

2. The Art of Electronics ISBN-13: 978-0521370950

3. All New Electronics Self Teaching Guide ISBN-13: 978-0470289617

External links

Circuits2]

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