Physics (electronics)

Electronics is the study of the flow of charge through various materials and devices such as, semiconductors, resistors, inductors, capacitors, nano-structures, and vacuum tubes. All applications of electronics involve the transmission of either information or power. Although considered to be a theoretical branch of physics, the design and construction of electronic circuits to solve practical problems is an essential technique in the fields of electronics engineering and computer engineering.
The study of new semiconductor devices and surrounding technology is sometimes considered a branch of physics. This article focuses on engineering aspects of electronics. Other important topics include electronic waste and occupational health impacts of semiconductor manufacturing.
Contents
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1 Overview of electronic systems and circuits
2 Electronic devices and components
3 Types of circuits
3.1 Analog circuits
3.2 Digital circuits
3.3 Mixed-signal circuits
4 Heat dissipation and thermal management
5 Noise
6 Electronics theory
7 Electronic test equipment
8 Computer aided design (CAD)
9 Construction methods
10 Electronics industry
11 Branch pages
12 See also
13 References
14 External links
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[edit] Overview of electronic systems and circuits

Commercial digital voltmeter checking a prototype
Electronic systems are used to perform a wide variety of tasks. The main uses of electronic circuits are:
The controlling and processing of data.
The conversion to/from and distribution of electric power.
Both these applications involve the creation and/or detection of electromagnetic fields and electric currents. While electrical energy had been used for some time prior to the late 19th century to transmit data over telegraph and telephone lines, development in electronics grew exponentially after the advent of radio.
One way of looking at an electronic system is to divide it into 3 parts:
Inputs – Electronic or mechanical sensors (or transducers). These devices take signals/information from external sources in the physical world (such as antennas or technology networks) and convert those signals/information into current/voltage or digital (high/low) signals within the system.
Signal processors – These circuits serve to manipulate, interpret and transform inputted signals in order to make them useful for a desired application. Recently, complex signal processing has been accomplished with the use of Digital Signal Processors.
Outputs – Actuators or other devices (such as transducers) that transform current/voltage signals back into useful physical form (e.g., by accomplishing a physical task such as rotating an electric motor).
For example, a television set contains these 3 parts. The television's input transforms a broadcast signal (received by an antenna or fed in through a cable) into a current/voltage signal that can be used by the device. Signal processing circuits inside the television extract information from this signal that dictates brightness, colour and sound level. Output devices then convert this information back into physical form. A cathode ray tube transforms electronic signals into a visible image on the screen. Magnet-driven speakers convert signals into audible sound.
[edit] Electronic devices and components
Main article: Electronic component
An electronic component is any indivisible electronic building block packaged in a discrete form with two or more connecting leads or metallic pads. Components are intended to be connected together, usually by soldering to a printed circuit board, to create an electronic circuit with a particular function (for example an amplifier, radio receiver, or oscillator). Components may be packaged singly (resistor, capacitor, transistor, diode etc.) or in more or less complex groups as integrated circuits (operational amplifier, resistor array, logic gate etc).
[edit] Types of circuits
[edit] Analog circuits
Main article: Analog circuits

Hitachi J100 adjustable frequency drive chassis.
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.
[edit] Digital circuits
Main article: 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" and "High". 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:
logic gates
Adders
Binary Multipliers
flip-flops
counters
registers
multiplexers
Schmitt triggers
Highly integrated devices:
microprocessors
microcontrollers
Application-specific integrated circuit(ASIC)
Digital signal processor (DSP)
Field Programmable Gate Array (FPGA)
[edit] Mixed-signal circuits
Main article: Mixed-signal integrated circuit
Mixed-signal circuits refers to integrated circuits (ICs) which have both analog circuits and digital circuits combined on a single semiconductor die or on the same circuit board. Mixed-signal circuits are becoming increasingly common. Mixed circuits contain both analog and digital components. Analog to digital converters and digital to analog converters are the primary examples. Other examples are transmission gates and buffers.
[edit] Heat dissipation and thermal management
Main article: Thermal management of electronic devices and systems
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.
[edit] Noise
Main article: electronic noise
Noise is associated with all electronic circuits. Noise is generally defined as any unwanted signal that is not present at the input of a circuit. Noise is not the same as signal distortion caused by a circuit.
[edit] Electronics theory
Main article: Mathematical methods in electronics
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.
[edit] Electronic test equipment
Main article: Electronic test equipment
Electronic test equipment is used to create stimulus signals and capture responses from electronic Devices Under Test (DUTs). In this way, the proper operation of the DUT can be proven or faults in the device can be traced and repaired.
Practical electronics engineering and assembly requires the use of many different kinds of electronic test equipment ranging from the very simple and inexpensive (such as a test light consisting of just a light bulb and a test lead) to extremely complex and sophisticated such as Automatic Test Equipment.
[edit] Computer aided design (CAD)
Main article: Electronic design automation
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 pcb design programs. Popular names in the EDA software world are NI Multisim, Cadence (ORCAD), Eagle PCB and Schematic, Mentor (PADS PCB and LOGIC Schematic), Altium (Protel), and many others.
[edit] Construction methods
Many different methods of connecting components have been used over the years. For instance, in the beginning point to point wiring using tag boards attached to chassis were used to connect various electrical innards. 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.
[edit] Electronics industry
Semiconductor sales leaders by year
[edit] Branch pages
Digital electronics
Analogue electronics
Microelectronics
Fuzzy electronics
Circuit Design
Integrated circuit
Optoelectronics
Semiconductor
Semiconductor device
[edit] See also

Electronics Portal
Circuit diagram
Computer engineering
Datasheet
E-waste
Electrical engineering
IEEE - the Institute of Electrical and Electronics Engineers
Mechatronics
Signal theory
Transducer
[edit] References
This article or section cites very few or no references or sources.Please help improve this article by adding citations to reliable sources. (help, get involved!)Any material not supported by sources may be challenged and removed at any time. This article has been tagged since January 2007.
[edit] External links

Wikibooks has more on the topic of
Electronics
Navy 1998 Navy Electricity and Electronics Training Series (NEETS)
DOE 1998 Electrical Science, Fundamentals Handbook, 4 vols.
Vol. 1, Basic Electrical Theory, Basic DC Theory
Vol. 2, DC Circuits, Batteries, Generators, Motors
Vol. 3, Basic AC Theory, Basic AC Reactive Components, Basic AC Power, Basic AC Generators
Vol. 4, AC Motors, Transformers, Test Instruments & Measuring Devices, Electrical Distribution Systems
Electronics Infoline Directory of Electronics Projects.
Electronics Tutorials at the Open Directory Project
Electronics Schematics at the Open Directory Project
DIY Audio Projects at the Open Directory Project
DIY Radio Projects at the Open Directory Project
Sources of Electronic Components at the Open Directory Project
Electronics and Electrical Books
Electronics Manufacturers Directory
Embedded Electronics
Electronics related books and projects
Lessons in Electric Circuits - A free series of textbooks on the subjects of electricity and electronics.
All About Circuits - Free illustrated on-line ebook and tutorials
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v • d • e
Major fields of technology

Hubble precisely measured the age of the universe. It found evidence of dark energy. It brought you images of distant galaxies in the young universe. And now, with the state-of-the-art instruments delivered by Servicing Mission 4 (SM4), the Hubble Space Telescope will look onto the universe with new eyes, surpassing even its previous vision.
Hubble was designed to be repaired and upgraded by astronauts, and these servicing missions have occurred several times since Hubble’s launch in 1990. SM4 has an ambitious program of activities. Over a series of five spacewalks, astronauts will replace worn-out telescope components, installing new batteries, new gyroscopes, a refurbished Fine Guidance Sensor, replacement thermal blankets, and more. It will significantly enhance Hubble's prowess with the installation of two new science instruments: the Wide Field Camera 3 and the Cosmic Origins Spectrograph. These upgrades will keep Hubble functioning at the pinnacle of astronomy well into the next decade.

Modern physics

The ability to describe light in electromagnetic terms helped serve as a springboard for Albert Einstein's publication of the theory of special relativity in 1905. This theory combined classical mechanics with Maxwell's equations. The theory of special relativity unifies space and time into a single entity, spacetime. Relativity prescribes a different transformation between reference frames than classical mechanics; this necessitated the development of relativistic mechanics as a replacement for classical mechanics. In the regime of low (relative) velocities, the two theories agree. Einstein built further on the special theory by including gravity into his calculations, and published his theory of general relativity in 1915.
One part of the theory of general relativity is Einstein's field equation. This describes how the stress-energy tensor creates curvature of spacetime and forms the basis of general relativity. Further work on Einstein's field equation produced results which predicted the Big Bang, black holes, and the expanding universe. Einstein believed in a static universe. He tried, and failed, to fix his equation to allow for this. By 1929, however, Edwin Hubble's astronomical observations suggested that the universe is expanding at a possibly exponential rate.

Marie Sklodowska-Curie
In 1895, Röntgen discovered X-rays, which turned out to be high-frequency electromagnetic radiation. Radioactivity was discovered in 1896 by Henri Becquerel, and further studied by Maria Sklodowska-Curie, Pierre Curie, and others. This initiated the field of nuclear physics.
In 1897, Joseph J. Thomson discovered the electron, the elementary particle which carries electrical current in circuits. In 1904, he proposed the first model of the atom, known as the plum pudding model. Its existence had been proposed in 1808 by John Dalton.
These discoveries revealed that the assumption of many physicists, that atoms were the basic unit of matter, was flawed, and prompted further study into the structure of atoms.

Ernest Rutherford
In 1911, Ernest Rutherford deduced from scattering experiments the existence of a compact atomic nucleus, with positively charged constituents dubbed protons. Neutrons, the neutral nuclear constituents, were discovered in 1932 by Chadwick. The equivalence of mass and energy (Einstein, 1905) was spectacularly demonstrated during World War II, as research was conducted by each side into nuclear physics, for the purpose of creating a nuclear bomb. The German effort, led by Heisenberg, did not succeed, but the Allied Manhattan Project reached its goal. In America, a team led by Fermi achieved the first man-made nuclear chain reaction in 1942, and in 1945 the world's first nuclear explosive was detonated at Trinity site, near Alamogordo, New Mexico. In 1900, Max Planck published his explanation of blackbody radiation. This equation assumed that radiators are quantized, which proved to be the opening argument in the edifice that would become quantum mechanics. By introducing discrete energy levels, Planck, Einstein, Niels Bohr, and others developed quantum theories to explain various anomalous experimental results.


Erwin Schrödinger
Quantum mechanics was formulated in 1925 by Heisenberg and in 1926 by Schrödinger and Paul Dirac, in two different ways, that both explained the preceding heuristic quantum theories. In quantum mechanics, the outcomes of physical measurements are inherently probabilistic; the theory describes the calculation of these probabilities. It successfully describes the behavior of matter at small distance scales. During the 1920s Schrödinger, Heisenberg, and Max Born were able to formulate a consistent picture of the chemical behavior of matter, a complete theory of the electronic structure of the atom, as a byproduct of the quantum theory.
Quantum field theory was formulated in order to extend quantum mechanics to be consistent with special relativity. It was devised in the late 1940s with work by Richard Feynman, Julian Schwinger, Sin-Itiro Tomonaga, and Freeman Dyson. They formulated the theory of quantum electrodynamics, which describes the electromagnetic interaction, and successfully explained the Lamb shift. Quantum field theory provided the framework for modern particle physics, which studies fundamental forces and elementary particles. Chen Ning Yang and Tsung-Dao Lee, in the 1950s, discovered an unexpected asymmetry in the decay of a subatomic particle. In 1954, Yang and Robert Mills then developed a class of gauge theories which provided the framework for understanding the nuclear forces (Yang, Mills 1954). The theory for the strong nuclear force was first proposed by Murray Gell-Mann. The electroweak force, the unification of the weak nuclear force with electromagnetism, was proposed by Sheldon Lee Glashow, Abdus Salam, and Steven Weinberg and confirmed in 1964 by James Watson Cronin and Val Fitch. This led to the so-called Standard Model of particle physics in the 1970s, which successfully describes all the elementary particles observed to date.
Quantum mechanics also provided the theoretical tools for condensed matter physics, whose largest branch is solid state physics. It studies the physical behavior of solids and liquids, including phenomena such as crystal structures, semiconductivity, and superconductivity. The pioneers of condensed matter physics include Felix Bloch, who created a quantum mechanical description of the behavior of electrons in crystal structures in 1928. The transistor was developed by physicists John Bardeen, Walter Houser Brattain, and William Bradford Shockley in 1947 at Bell Laboratories. The two themes of the twentieth century, general relativity and quantum mechanics, appear inconsistent with each other. General relativity describes the universe on the scale of planets and solar systems, while quantum mechanics operates on sub-atomic scales. This challenge is being attacked by string theory, which treats spacetime as composed, not of points, but of one-dimensional objects, strings. Strings have properties similar to a common string (e.g., tension and vibration). The theories yield promising, but not yet testable, results. The search for experimental verification of string theory is in progress.

Physics

Physics (Greek: φύσις (phúsis), "nature" and φυσικῆ (phusiké), "knowledge of nature") is the branch of science concerned with the fundamental laws of the universe. In the field of physics, the elementary constituents of the universe—matter, energy, space, and time—and their interactions are studied; and systems best understood in terms of these fundamental principles and laws are analyzed. "Physics" (once spelled physike in imitation of Aristotle) formerly consisted of the study of its counterpart, natural philosophy, from classical times until the separation of modern physics from philosophy as a positive science during the nineteenth century.

>Introduction

Since antiquity, natural philosophers have sought to explain physical phenomena and the nature of matter, but the emergence of physics as a modern science began with the scientific revolution of the 16th and 17th centuries and continued through the dawn of modern physics in the early 20th century. The field has since continued to expand, with a growing body of research leading to discoveries such as the Standard Model of fundamental particles and a detailed history of the universe, along with revolutionary new technologies like nuclear weapons and semiconductors. Research today progresses on a vast array of topics, including high-temperature superconductivity, quantum computing, the Higgs boson, dark matter and dark energy, and the attempt to develop a theory of quantum gravity. Firmly grounded in observation and experiment, with a rich set of theories expressed in elegant mathematical language, physics has made a multitude of contributions to philosophy, science, and technology.

Discoveries in physics resonate throughout the natural sciences; physics has thus been described as the "fu