Cognitive anthropology

From Wikipedia, the free encyclopedia

en.wikipedia.org/wiki/Cognitive_anthropology 

Cognitive anthropology is a subfield of anthropology influenced by Linguistic anthropology, cultural anthropology, and biological anthropology in which scholars seek to explain patterns of shared knowledge, cultural innovation, and transmission over time and space using the methods and theories of the cognitive sciences (especially experimental psychology and cognitive psychology) often through close collaboration with historians, ethnographers, archaeologists, linguists, musicologists, and other specialists engaged in the description and interpretation of cultural forms. Cognitive anthropology is concerned with what people from different groups know and how that implicit knowledge, in the sense of what they think subconsciously, changes the way people perceive and relate to the world around them.

History

Cognitive anthropology arose as part of efforts designed to understand the relationship between language and thought, with linguistic anthropologists of North America in the 1950s spearheading the effort to approach cognition in cultural contexts, rather than as an effort to identify or assume cognitive universals.

Cognitive anthropology became a current paradigm of anthropology under the new ethnography or ethnoscience paradigm that emerged in American anthropology toward the end of the 1950s.

Scope

Cognitive anthropology studies a range of domains including folk taxonomies, the interaction of language and thought, and cultural models.

From a linguistics stand-point, cognitive anthropology uses language as the doorway to study cognition. Its general goal is to break language down to find commonalities in different cultures and the ways people perceive the world. Linguistic study of cognitive anthropology may be broken down into three subfields: semantics, syntactics, and pragmatics.

Cognitive anthropology is separated in two categories, thought in society/culture and language. Thought is concerned with the procedure and outcome of thoughts. The thinking process in cognitive anthropology puts the importance of culture at the center of examining thoughts. Cognitive anthropologists believe that cultural meanings arise when people learn, create, interpret and apply these collective representations. Reapplication and representations reinforce the experienced patterns through the process of implementing appropriateness and relevance, contain the elements for cognitive reorganization and creativity in behavior and understanding.

In cognitive anthropology language is seen as an important source for analyzing thinking processes. Cognitive anthropology analyzes cultural views with lexicons as the primary source of data that researches search for definite beliefs, implicit understandings and category systems.

Methods

Cognitive anthropology uses quantitative measures as well as the traditional ethnographic methods of cultural anthropology in order to study culture. Because of the field's interest in determining shared knowledge, consensus analysis has been used as its most widely used statistical measure.

One of the techniques used is Cultural Network Analysis, the drawing of networks of interrelated ideas that are widely shared among members of a population. Recently there has been some interchange between cognitive anthropologists and those working in artificial intelligence.

Relation with cognitive science

Cognitive anthropology intersects with several other fields within its parent cultural anthropology sphere. Whereas cultural anthropologists had always sought to identify and organize certain salient facets of culture, cognitive anthropologists appreciate the reflexive nature of their study. Instead of analyzing facets of culture as they appear to the anthropologist, they place special emphasis on emic viewpoints of culture to understand what motivates different populations, eventually coming to an understanding of universal cognition. These goals form the basis of the argument merging cognitive anthropology and cognitive science.

Cognitive anthropology is linked to psychology because studying the way social groups reason and categorize raises questions about the basic nature of cognitive processes.

Advocacy

Advocate and presidential researcher Giovanni Bennardo put forth three categories of data in 2013 that warrant this grouping. Cognitive anthropologists gather ethnographic, linguistic, and experimental data, which is then analyzed quantitatively. For example, medical rituals provide more direct data that informs linguistic analysis and a greater insight into cognitive motivations, hence the field’s similarity to linguistic relativism. To advocates, the mind is a cultural facet (as is kinship to the pioneering cultural anthropologist) that generates language, which provides insight into human cognition.

Other advocates for cognitive anthropology’s categorization with cognitive science have pointed out that cognitive psychology fails to encompass several fields that cognitive anthropology does, hence its pivotal role in cognitive science. Professor of Psychology at University of Connecticut, James S. Boster, points out in the Journal of the Cognitive Science Society that while cognitive psychology studies a human’s thought process, cognitive anthropology studies what exactly different humans ponder—what they sense and perceive of their own culture and surroundings in different settings.

Criticism

There has been longtime conflict between cognitive scientists and cognitive anthropologists on the intersection of their respective fields. The grouping has received much backlash in the literature, such as from Edward Evans-Pritchard on the basis of methodology and subject matter.

Cognitive psychologists have criticized cognitive anthropologists for their chaotic research methods, such as forming instruments of observation and data acquisition using language that natives use in their interviews with fieldworkers. "CA has been alienated from the rest of cultural anthropology because it is seen as too quantitative and scientific for the prevailing post‐modern aesthetic, while at the same time seen as too ethnographic and natural historical for the tastes of CP."

Some cognitive scientists have devalued anthropology's influence in the cognitive sciences, which was extensively discussed by Sieghard Beller, Andrea Bender, and Douglas Medin in the Journal of the Cognitive Science Society. In their widely cited journal article, they attribute this rejection to cognitive anthropology's lack of credibility as a subset of the psychological sciences, focus on common narratives throughout different cultures rather than on the individual mind, and difficulty of getting published. "They strive for insights that explain something about the human mind in general and therefore consider cross‐cultural comparisons as just one means to test assumptions on universals."

Critics have also disputed the scientific nature of cognitive anthropology in general and argued that it studies content of thought rather than process, which cognitive science centers on. Resistance from more established subfields of cultural anthropology has historically restricted resources and tenure for cognitive anthropologists.

Feminist sex wars

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Feminist_sex_wars

  

The feminist sex wars, also known as the lesbian sex wars, sex wars or porn wars, are collective debates amongst feminists regarding a number of issues broadly relating to sexuality and sexual activity. Differences of opinion on matters of sexuality deeply polarized the feminist movement, particularly leading feminist thinkers, in the late 1970s and early 1980s and continue to influence debate amongst feminists to this day.

The sides were characterized by anti-porn feminist and sex-positive feminist groups with disagreements regarding sexuality, including pornography, erotica, prostitution, lesbian sexual practices, the role of transgender women in the lesbian community, sadomasochism and other sexual matters. The feminist movement was deeply divided as a result of these debates. Many historians view the feminist sex wars as having been the end of the second-wave feminist era (which began c. 1963) as well as the herald of the third wave (which began in the early 1990s).

Two opposing views

Ariel Levy described the Dworkin-MacKinnon Ordinance as "the single most divisive issue" of the feminist sex wars. Dworkin captured the spirit of the anti-pornography side of the debate in her famous utterance: "I'm a radical feminist, not the fun kind."

The two sides became labelled anti-pornography feminists and sex-positive feminists.

Anti-pornography feminists

In 1976, Andrea Dworkin organized demonstrations against the film Snuff in New York, but attempts to start an organization to continue the feminist anti-pornography campaign failed. Efforts were more successful in Los Angeles, where Women Against Violence Against Women was founded in response to Snuff in 1976; they campaigned against the Rolling Stones' 1976 album Black and Blue. The U.S. anti-pornography movement gained ground with the founding of Women Against Violence in Pornography and Media (WAVPM) in 1977 in San Francisco, following a 1976 conference on violence against women held by local women's centers. Early members included Susan Griffin, Kathleen Barry, and Laura Lederer.

WAVPM organised the first national conference on pornography in San Francisco in 1978 which included the first Take Back the Night march. The conference led to anti-pornography feminists organizing in New York in 1979 under the banner of Women Against Pornography (WAP), and to similar organizations and efforts being created across the United States. In 1983, Page Mellish, a one-time member of WAVPM and of WAP, founded Feminists Fighting Pornography to focus on political activism seeking legal changes to limit the porn industry. Andrea Dworkin and Catharine MacKinnon wanted civil laws restricting pornography and to this end drafted the Antipornography Civil Rights Ordinance, also known as the Dworkin–MacKinnon Ordinance.

In her article Can We End the Feminist ‘Sex Wars’ Now? Comments on Linda Martín Alcoff, Rape and Resistance: Understanding the Complexities of Sexual Violation, Susan J. Brison explores the varying opinions of Catherine MacKinnon and Michel Foucault. MacKinnon states that the patriarchy is to blame for issues like exploitation and sex trafficking. She further claims that men hold authority, and the way to overcome this is to take legal action and hold the exploiters accountable. Foucault argues that sexuality is a social construct. Opposing MacKinnon’s argument, legal action does not work if the issue is deeply rooted in the structure of society. According to Brinson, combining these two ideologies could potentially end feminist sex wars once and for all. Addressing the institutional issues while applying appropriate legal action would create a more feminist way to help affected sex workers.

Sex-positive feminists

The terms pro-sex feminism and, later, sex-positive feminism were inspired by Ellen Willis.

From 1979, feminist journalist Ellen Willis was one of the early voices criticizing anti-pornography feminists for what she saw as sexual puritanism, moral authoritarianism and a threat to free speech. Her 1981 essay, Lust Horizons: Is the Women's Movement Pro-Sex? is the origin of the term, "pro-sex feminism". In response to the anti-pornography strand of feminism, sex-positive feminists promoted sex as an avenue of pleasure for women, seeing anti-pornography positions as aligned to the political right-wing’s war on recreational sex and pornography. Early sex positive groups included Samois, founded in San Francisco in 1978, whose early members included Gayle Rubin and Pat Califia, and the Lesbian Sex Mafia, founded by Dorothy Allison and Jo Arnone in New York in 1981. The Feminist Anti-Censorship Taskforce (FACT) was set up in 1984 by Ellen Willis in response to the Dworkin–MacKinnon Ordinance; in 1989 Feminists Against Censorship formed in the UK, its members including Avedon Carol; and Feminists for Free Expression formed in the United States in 1992 by Marcia Pally, with founding members including Nadine Strossen, Joan Kennedy Taylor, Veronica Vera and Candida Royalle. Philosopher Amin R. Yacoub argues that defending sex work and the autonomy of those in the industry is the ethical thing to do. This view continues to claim that as long as the work is consensual, this form of work is legitimate with a positive consequence of fighting the patriarchy. Advocating for the rights of those in the industry gives them potential for autonomy and empowerment.

Key events

In October 1980, the National Organization for Women identified what became known as the "Big Four" through declaring that "Pederasty, pornography, sadomasochism and public sex" were about "exploitation, violence or invasion of privacy" and not "sexual preference or orientation". One of the more memorable clashes between the pro-sex and anti-porn feminists occurred at the 1982 Barnard Conference on Sexuality. Anti-pornography feminists were excluded from the events’ planning committee, so they staged rallies outside the conference to show their disdain.

Debates

The two sides of the feminist sex wars clashed over a number of issues, resulting in intense debates held both in person and in various media.

Pornography debate

Main article: Feminist views on pornography

Toward the end of the 1970s, much of the discourse in the feminist movement shifted from the discussion of lesbian feminism to focus on the new topic of sexuality. One of the primary concerns with sexuality was the issue of pornography, which caused a great divide among feminists. The two recognized sides of the debate were anti-pornography feminism and "pro-sex" feminism. One of the major influences of anti-pornography feminism was its predecessor, lesbian feminism. Anti-pornography movements developed from fundamental arguments displayed by lesbianism, such as the notion of patriarchal sexual relations. Ellen Willis described these relations as being "based on male power backed by force." From this perspective, pornography is created exclusively for men by men and is a direct reflection of the man-dominant paradigm surrounding sexual relations. Another idea taken from lesbian feminism by anti-pornography groups was that sexuality is about creating a compassionate bond and a lasting relation with another person, contrary to the belief of the purely physical nature of sex.

In her book, Pornography: Men Possessing Women, Andrea Dworkin argued that the theme of pornography is male dominance and as a result it is intrinsically harmful to women and their well-being. Dworkin believed that pornography is not only damaging in its production but also in its consumption, since the viewer will mentally internalize pornography's misogynistic portrayal of women. Robin Morgan summarized the view of anti-pornography feminists that pornography and violence against women are linked in her statement, "pornography is the theory, rape is the practice".

Jackie O’Brien criticizes the use of paywalls in the pornography industry. Pornography filters possibly take away autonomy from the sex workers. Their profits go to the companies they work for, which potentially means exploitation. These paywalls are meant to protect minors. However, a consequence is that the content from the sex workers gets used and distributed by third parties or private platforms. The content barricade does not address the structural roots of the issues in the porn industry. Anything surrounding this argument comes with nuance. It is difficult to find a middle ground between protecting the public from explicit content while protecting the rights of women in the industry.

The anti-pornography movement has been criticised by sex-positive feminists as a repression of sexuality and a move towards censorship. In her article, Thinking Sex: Notes for a Radical Theory of the Politics of Sexuality, Gayle Rubin characterizes sex liberation as a feminist goal and denounces the idea that anti-pornography feminists speak collectively for all of feminism. She offers the notion that what is needed is a theory of sexuality separate from feminism. In XXX: A Woman's Right to Pornography, Wendy McElroy summarizes the sex-positive perspective as "the benefits pornography provides to women far outweigh any of its disadvantages".

The pornography debate among radical and libertarian feminists has focused on the depictions of female sexuality in relation to male sexuality in this type of media. Radical feminists emphasize that pornography illustrates objectification and normalization of sexual violence through presentation of specific acts. In contrast, libertarian feminists are concerned with the stigmatization of sexual minorities and the limited right to practice sexual choice that would be hindered without pornography.

Sadomasochism debate

Main article: Feminist views on BDSM

The main focus of the sex wars' debate on sadomasochism and other BDSM practices took place in San Francisco. Women Against Violence in Pornography and Media (WAVPM) was founded there in 1977. Its first political action was to picket a live show at a strip club featuring women performing sadomasochistic acts on each other, in line with its stated aim to end all portrayals of women being "bound, raped, tortured, killed or degraded for sexual stimulation or pleasure". As well as campaigning against pornography, WAVPM were also strongly opposed to BDSM, seeing it as ritualized violence against women and opposed its practice within the lesbian community. In 1978 Samois was formed, an organization for women in the BDSM community who saw their sexual practices as consistent with feminist principles. Several black lesbian feminists have written on this topic, including Audre Lorde, Alice Walker, Darlene Pagano, Karen Sims, and Rose Mason, condemning sadomasochism as an often racist practice, insensitive to the black female experience.

Prostitution debate

See also: Feminist views on prostitution

Another debate of the feminist sex wars centered on prostitution. The women in the anti-pornography camp argued against prostitution, claiming it is forced on women who have no alternatives. Meanwhile, sex-positive feminists argued that this position ignored the agency of women who chose sex work, viewing prostitution as not inherently based on the exploitation of women. Carol Leigh notes that "The Prostitutes rights movement of the early 1970s evolved directly from the women's movement", but adds: "The women's movement in the U.S. has always been ambivalent about prostitutes".

In her article The Sex Wars: Prostitution, Carceral Feminists, and the Consolidation of Police Power, Jessica R. Piley explains dominant feminists and how they tried to end prostitution for good. These feminist collaborated with law enforcement. In Sex Work and the Law, Anne Gray Fisher reframes the debate in terms of socioeconomic class, coming to the conclusion that although feminists on both sides of the debate had noble intentions to end the dangers of sex work, neither addressed the problems faced by marginalized communities. In Fisher's view, enforcement of anti-prostitution laws especially targeted Black, impoverished, and LGBT sex workers, while legalization strategies have primarily served to benefit white, affluent, and educated women.

Effects

The polarization of feminist ideology during the sex wars has had wide-ranging effects. Examples include: "The confusion in the interpretation of the definition of human trafficking is a consequence of opposing feminist views on prostitution."

According to New Directions in Sex Therapy, the fields of sexology and sex therapy were made to keep a "low profile" during the 1970s and 1980s due to attacks from social conservatives and anti-pornography feminists.

Third-wave feminists' views

Third-wave feminist writings promote personal, individualized views on the gender-related issues focused on during the feminist sex wars, such as prostitution, pornography and sadomasochism. Items such as sex objects and porn, identified by some second-wave feminists as instruments of oppression are now no longer being exclusively used by men but also by women. Feminist critic Teresa de Lauretis sees the sex wars not in terms of polarized sides but as reflecting a third wave feminism inherently embodying difference, which may include conflicting and competing drives. Meanwhile, critic Jana Sawicki rejects both the polarized positions, seeking a third way that is neither morally dogmatic nor uncritically libertarian.

Sheila Rowbotham and the other socialist feminists who dominated the British women's movement saw women's liberation as inextricably linked to the demolition of capitalism. But it also required—and this is where they diverged from the Old Guard—a reconsideration of common patterns of life, such as sex, love, housework, and childrearing.

Electronics

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Electronics

Modern surface-mount electronic components on a printed circuit board, with a large integrated circuit at the top

Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other electrically charged particles. It is a subfield of physics and electrical engineering which uses active devices such as transistors, diodes, and integrated circuits to control and amplify the flow of electric current and to convert it from one form to another, such as from alternating current (AC) to direct current (DC) or from analog signals to digital signals.

Electronic devices have significantly influenced the development of many aspects of modern society, such as telecommunications, entertainment, education, health care, industry, and security. The main driving force behind the advancement of electronics is the semiconductor industry, which continually produces ever-more sophisticated electronic devices and circuits in response to global demand. The semiconductor industry is one of the global economy's largest and most profitable industries, with annual revenues exceeding $481 billion in 2018. The electronics industry also encompasses other branches that rely on electronic devices and systems, such as e-commerce, which generated over $29 trillion in online sales in 2017.

History and development

See also: History of electronic engineering and Timeline of electrical and electronic engineering

One of the earliest Audion radio receivers, constructed by De Forest in 1914

Karl Ferdinand Braun´s development of the crystal detector, the first semiconductor device, in 1874 and the identification of the electron in 1897 by Sir Joseph John Thomson, along with the subsequent invention of the vacuum tube which could amplify and rectify small electrical signals, inaugurated the field of electronics and the electron age. Practical applications started with the invention of the diode by Ambrose Fleming and the triode by Lee De Forest in the early 1900s, which made the detection of small electrical voltages, such as radio signals from a radio antenna, practicable.

Vacuum tubes (thermionic valves) were the first active electronic components which controlled current flow by influencing the flow of individual electrons, and enabled the construction of equipment that used current amplification and rectification to give us radio, television, radar, long-distance telephony and much more. The early growth of electronics was rapid, and by the 1920s, commercial radio broadcasting and telecommunications were becoming widespread and electronic amplifiers were being used in such diverse applications as long-distance telephony and the music recording industry.

The next big technological step took several decades to appear, when the first working point-contact transistor was invented by John Bardeen and Walter Houser Brattain at Bell Labs in 1947. However, vacuum tubes continued to play a leading role in the field of microwave and high power transmission as well as television receivers until the middle of the 1980s. Since then, solid-state devices have all but completely taken over. Vacuum tubes are still used in some specialist applications such as high power RF amplifiers, cathode-ray tubes, specialist audio equipment, guitar amplifiers and some microwave devices.

In April 1955, the IBM 608 was the first IBM product to use transistor circuits without any vacuum tubes and is believed to be the first all-transistorized calculator to be manufactured for the commercial market. The 608 contained more than 3,000 germanium transistors. Thomas J. Watson Jr. ordered all future IBM products to use transistors in their design. From that time on transistors were almost exclusively used for computer logic circuits and peripheral devices. However, early junction transistors were relatively bulky devices that were difficult to manufacture on a mass-production basis, which limited them to a number of specialised applications.

The MOSFET was invented at Bell Labs between 1955 and 1960. It was the first truly compact transistor that could be miniaturised and mass-produced for a wide range of uses. Its advantages include high scalability, affordability, low power consumption, and high density. It revolutionized the electronics industry, becoming the most widely used electronic device in the world. The MOSFET is the basic element in most modern electronic equipment.

As the complexity of circuits grew, problems arose. One problem was the size of the circuit. A complex circuit like a computer was dependent on speed. If the components were large, the wires interconnecting them must be long. The electric signals took time to go through the circuit, thus slowing the computer.^[26] The invention of the integrated circuit by Jack Kilby and Robert Noyce solved this problem by making all the components and the chip out of the same block (monolith) of semiconductor material. The circuits could be made smaller, and the manufacturing process could be automated. This led to the idea of integrating all components on a single-crystal silicon wafer, which led to small-scale integration (SSI) in the early 1960s, and then medium-scale integration (MSI) in the late 1960s, followed by VLSI. In 2008, billion-transistor processors became commercially available.

Subfields

• Analog electronics
• Audio electronics
• Avionics
• Bioelectronics
• Circuit design
• Digital electronics
• Electronic components
• Embedded systems
• Integrated circuits
• Microelectronics
• Nanoelectronics
• Optoelectronics
• Power electronics
• Printed circuit boards
• Semiconductor devices
• Sensors
• Telecommunications

Devices and components

Main article: Electronic component

Various electronic components

An electronic component is any component in an electronic system either active or passive. Components are connected together, usually by being soldered to a printed circuit board (PCB), to create an electronic circuit with a particular function. Components may be packaged singly, or in more complex groups as integrated circuits. Passive electronic components are capacitors, inductors, resistors, whilst active components are such as semiconductor devices; transistors and thyristors, which control current flow at electron level.

Types of circuits

Electronic circuit functions can be divided into two function groups: analog and digital. A particular device may consist of circuitry that has either or a mix of the two types. Analog circuits are becoming less common, as many of their functions are being digitized.

Analog circuits

Main article: Analog electronics

Analog circuits use a continuous range of voltage or current for signal processing, as opposed to the discrete levels used in digital circuits. Analog circuits were common throughout an electronic device in the early years in devices such as radio receivers and transmitters. Analog electronic computers were valuable for solving problems with continuous variables until digital processing advanced.

As semiconductor technology developed, many of the functions of analog circuits were taken over by digital circuits, and modern circuits that are entirely analog are less common; their functions being replaced by hybrid approach which, for instance, uses analog circuits at the front end of a device receiving an analog signal, and then use digital processing using microprocessor techniques thereafter.

Sometimes it may be difficult to classify some circuits that have elements of both linear and non-linear operation. An example is the voltage comparator which receives a continuous range of voltage but only outputs 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.

Analog circuits are still widely used for signal amplification, such as in the entertainment industry, and conditioning signals from analog sensors, such as in industrial measurement and control.

Digital circuits

Main article: Digital electronics

Digital circuits are electric circuits based on discrete voltage levels. Digital circuits use Boolean algebra and are the basis of all digital computers and microprocessor devices. They range from simple logic gates to large integrated circuits, employing millions of such gates.

Digital circuits use a binary system with two voltage levels labelled "0" and "1" to indicated logical status. Often logic "0" will be a lower voltage and referred to as "Low" while logic "1" is referred to as "High". However, some systems use the reverse definition ("0" is "High") or are current based. Quite often the logic designer may reverse these definitions from one circuit to the next as they see fit to facilitate their design. The definition of the levels as "0" or "1" is arbitrary.

Ternary (with three states) logic has been studied, and some prototype computers made, but have not gained any significant practical acceptance. Universally, Computers and Digital signal processors are constructed with digital circuits using Transistors such as MOSFETs in the electronic logic gates to generate binary states.

A selection of logic gates, used extensively in digital electronics

• Logic gates
• Adders
• Flip-flops
• Counters
• Registers
• Multiplexers
• Schmitt triggers

Highly integrated devices:

• Memory chip
• Microprocessors
• Microcontrollers
• Application-specific integrated circuit (ASIC)
• Digital signal processor (DSP)
• Field-programmable gate array (FPGA)
• Field-programmable analog array (FPAA)
• System on chip (SOC)

Design

Electronic systems design deals with the multi-disciplinary design issues of complex electronic devices and systems, such as mobile phones and computers. The subject covers a broad spectrum, from the design and development of an electronic system (new product development) to assuring its proper function, service life and disposal. Electronic systems design is therefore the process of defining and developing complex electronic devices to satisfy specified requirements of the user.

Due to the complex nature of electronics theory, laboratory experimentation is an important part of the development of electronic devices. These experiments are used to test or verify the engineer's design and detect errors. Historically, electronics labs have consisted of electronics devices and equipment located in a physical space, although in more recent years the trend has been towards electronics lab simulation software, such as CircuitLogix, Multisim, and PSpice.

Computer-aided design

Main article: Electronic design automation

Today's electronics engineers have the ability to design circuits using premanufactured building blocks such as power supplies, semiconductors (i.e. semiconductor devices, 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), EAGLE PCB^[32] and Schematic, Mentor (PADS PCB and LOGIC Schematic), Altium (Protel), LabCentre Electronics (Proteus), gEDA, KiCad and many others.

Negative qualities

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. Heat dissipation is mostly achieved by passive conduction/convection. Means to achieve greater dissipation include heat sinks and fans for air cooling, and other forms of computer cooling such as water cooling. These techniques use convection, conduction, and radiation of heat energy.

Noise

Main article: Electronic noise

Electronic 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. Noise is associated with all electronic circuits. Noise may be electromagnetically or thermally generated, which can be decreased by lowering the operating temperature of the circuit. Other types of noise, such as shot noise cannot be removed as they are due to limitations in physical properties.

Packaging methods

Main article: Electronic packaging

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 wrap were other methods used. Most modern day electronics now use printed circuit boards made of materials such as FR4, or the cheaper (and less hard-wearing) Synthetic Resin Bonded Paper (SRBP, also known as Paxoline/Paxolin (trade marks) and FR2) – characterised by its brown colour. Health and environmental concerns associated with electronics assembly have gained increased attention in recent years, especially for products destined to go to European markets.

Through-hole devices mounted on the circuit board of a mid-1980s home computer. Axial-lead devices are at upper left, while blue radial-lead capacitors are at upper right.

Electrical components are generally mounted in the following ways:

• Through-hole (sometimes referred to as 'Pin-Through-Hole')
• Surface mount
• Chassis mount
• Rack mount
• LGA/BGA/PGA socket

Industry

Main article: Electronics industry

Further information: Consumer electronics, List of best-selling electronic devices, and Semiconductor industry

The electronics industry consists of various branches. The central driving force behind the entire electronics industry is the semiconductor industry, which has annual sales of over $481 billion as of 2018. The largest industry sector is e-commerce, which generated over $29 trillion in 2017. The most widely manufactured electronic device is the metal-oxide-semiconductor field-effect transistor (MOSFET), with an estimated 13 sextillion MOSFETs having been manufactured between 1960 and 2018. In the 1960s, U.S. manufacturers were unable to compete with Japanese companies such as Sony and Hitachi who could produce high-quality goods at lower prices. By the 1980s, however, U.S. manufacturers became the world leaders in semiconductor development and assembly.

However, during the 1990s and subsequently, the industry shifted overwhelmingly to East Asia (a process begun with the initial movement of microchip mass-production there in the 1970s), as plentiful, cheap labor, and increasing technological sophistication, became widely available there.

Over three decades, the United States' global share of semiconductor manufacturing capacity fell, from 37% in 1990, to 12% in 2022. America's pre-eminent semiconductor manufacturer, Intel Corporation, fell far behind its subcontractor Taiwan Semiconductor Manufacturing Company (TSMC) in manufacturing technology.

By that time, Taiwan had become the world's leading source of advanced semiconductors—followed by South Korea, the United States, Japan, Singapore, and China.

Important semiconductor industry facilities (which often are subsidiaries of a leading producer based elsewhere) also exist in Europe (notably the Netherlands), Southeast Asia, South America, and Israel.

Band gap

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Band_gap 

Graph of carbon atoms being brought together to form a diamond crystal, demonstrating formation of the electronic band structure and band gap. The right graph shows the energy levels as a function of the spacing between atoms. When far apart (right side of graph) all the atoms have discrete valence orbitals p and s with the same energies. However, when the atoms come closer (left side), their electron orbitals begin to spatially overlap and hybridize into N molecular orbitals each with a different energy, where N is the number of atoms in the crystal. Since N is such a large number, adjacent orbitals are extremely close together in energy so the orbitals can be considered a continuous energy band. At the actual diamond crystal cell size (denoted by a), two bands are formed, called the valence and conduction bands, separated by a 5.5 eV band gap. The Pauli exclusion principle limits the number of electrons in a single orbital to two, and the bands are filled beginning with the lowest energy.

In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to the energy difference (often expressed in electronvolts) between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. It is the energy required to promote an electron from the valence band to the conduction band. The resulting conduction-band electron (and the electron hole in the valence band) are free to move within the crystal lattice and serve as charge carriers to conduct electric current. It is closely related to the HOMO/LUMO gap in chemistry. If the valence band is completely full and the conduction band is completely empty, then electrons cannot move within the solid because there are no available states. If the electrons are not free to move within the crystal lattice, then there is no generated current due to no net charge carrier mobility. However, if some electrons transfer from the valence band (mostly full) to the conduction band (mostly empty), then current can flow (see carrier generation and recombination). Therefore, the band gap is a major factor determining the electrical conductivity of a solid. Substances having large band gaps (also called "wide" band gaps) are generally insulators, those with small band gaps (also called "narrow" band gaps) are semiconductors, and conductors either have very small band gaps or none, because the valence and conduction bands overlap to form a continuous band.

It is possible to produce laser induced insulator-metal transitions which have already been experimentally observed in some condensed matter systems, like thin films of C₆₀, doped manganites, or in vanadium sesquioxide V₂O₃. These are special cases of the more general metal-to-nonmetal transitions phenomena which were intensively studied in the last decades. A one-dimensional analytic model of laser induced distortion of band structure was presented for a spatially periodic (cosine) potential. This problem is periodic both in space and time and can be solved analytically using the Kramers-Henneberger co-moving frame. The solutions can be given with the help of the Mathieu functions.

In semiconductor physics

Semiconductor band structure.

Every solid has its own characteristic energy-band structure. This variation in band structure is responsible for the wide range of electrical characteristics observed in various materials. Depending on the dimension, the band structure and spectroscopy can vary. The different types of dimensions are as listed: one dimension, two dimensions, and three dimensions.

In semiconductors and insulators, electrons are confined to a number of bands of energy, and forbidden from other regions because there are no allowable electronic states for them to occupy. The term "band gap" refers to the energy difference between the top of the valence band and the bottom of the conduction band. Electrons are able to jump from one band to another. However, in order for a valence band electron to be promoted to the conduction band, it requires a specific minimum amount of energy for the transition. This required energy is an intrinsic characteristic of the solid material. Electrons can gain enough energy to jump to the conduction band by absorbing either a phonon (heat) or a photon (light).

A semiconductor is a material with an intermediate-sized, non-zero band gap that behaves as an insulator at T=0K, but allows thermal excitation of electrons into its conduction band at temperatures that are below its melting point. In contrast, a material with a large band gap is an insulator. In conductors, the valence and conduction bands may overlap, so there is no longer a bandgap with forbidden regions of electronic states.

The conductivity of intrinsic semiconductors is strongly dependent on the band gap. The only available charge carriers for conduction are the electrons that have enough thermal energy to be excited across the band gap and the electron holes that are left off when such an excitation occurs.

Band-gap engineering is the process of controlling or altering the band gap of a material by controlling the composition of certain semiconductor alloys, such as GaAlAs, InGaAs, and InAlAs. It is also possible to construct layered materials with alternating compositions by techniques like molecular-beam epitaxy. These methods are exploited in the design of heterojunction bipolar transistors (HBTs), laser diodes and solar cells.

The distinction between semiconductors and insulators is a matter of convention. One approach is to think of semiconductors as a type of insulator with a narrow band gap. Insulators with a larger band gap, usually greater than 4 eV, are not considered semiconductors and generally do not exhibit semiconductive behaviour under practical conditions. Electron mobility also plays a role in determining a material's informal classification.

The band-gap energy of semiconductors tends to decrease with increasing temperature. When temperature increases, the amplitude of atomic vibrations increase, leading to larger interatomic spacing. The interaction between the lattice phonons and the free electrons and holes will also affect the band gap to a smaller extent.^[8] The relationship between band gap energy and temperature can be described by Varshni's empirical expression (named after Y. P. Varshni),

${\displaystyle E_g(T)=E_g(0)-\frac{\alpha T^2}{T+\beta }}$, where E_g(0), α and β are material constants.

Furthermore, lattice vibrations increase with temperature, which increases the effect of electron scattering. Additionally, the number of charge carriers within a semiconductor will increase, as more carriers have the energy required to cross the band-gap threshold and so conductivity of semiconductors also increases with increasing temperature. The external pressure also influences the electronic structure of semiconductors and, therefore, their optical band gaps.

In a regular semiconductor crystal, the band gap is fixed owing to continuous energy states. In a quantum dot crystal, the band gap is size dependent and can be altered to produce a range of energies between the valence band and conduction band. It is also known as quantum confinement effect.

Band gaps can be either direct or indirect, depending on the electronic band structure of the material.

It was mentioned earlier that the dimensions have different band structure and spectroscopy. For non-metallic solids, which are one dimensional, have optical properties that are dependent on the electronic transitions between valence and conduction bands. In addition, the spectroscopic transition probability is between the initial and final orbital and it depends on the integral. φ_i is the initial orbital, φ_f is the final orbital, ʃ φ_f^*ûεφ_i is the integral, ε is the electric vector, and u is the dipole moment.

Two-dimensional structures of solids behave because of the overlap of atomic orbitals. The simplest two-dimensional crystal contains identical atoms arranged on a square lattice. Energy splitting occurs at the Brillouin zone edge for one-dimensional situations because of a weak periodic potential, which produces a gap between bands. The behavior of the one-dimensional situations does not occur for two-dimensional cases because there are extra freedoms of motion. Furthermore, a bandgap can be produced with strong periodic potential for two-dimensional and three-dimensional cases.

Direct and indirect band gap

Main article: Direct and indirect bandgaps

Based on their band structure, materials are characterised with a direct band gap or indirect band gap. In the free-electron model, k is the momentum of a free electron and assumes unique values within the Brillouin zone that outlines the periodicity of the crystal lattice. If the momentum of the lowest energy state in the conduction band and the highest energy state of the valence band of a material have the same value, then the material has a direct bandgap. If they are not the same, then the material has an indirect band gap and the electronic transition must undergo momentum transfer to satisfy conservation. Such indirect "forbidden" transitions still occur, however at very low probabilities and weaker energy. For materials with a direct band gap, valence electrons can be directly excited into the conduction band by a photon whose energy is larger than the bandgap. In contrast, for materials with an indirect band gap, a photon and phonon must both be involved in a transition from the valence band top to the conduction band bottom, involving a momentum change. Therefore, direct bandgap materials tend to have stronger light emission and absorption properties and tend to be better suited for photovoltaics (PVs), light-emitting diodes (LEDs), and laser diodes; however, indirect bandgap materials are frequently used in PVs and LEDs when the materials have other favorable properties.

Light-emitting diodes and laser diodes

Main article: Light-emitting diode

LEDs and laser diodes usually emit photons with energy close to and slightly larger than the band gap of the semiconductor material from which they are made. Therefore, as the band gap energy increases, the LED or laser color changes from infrared to red, through the rainbow to violet, then to UV.

Photovoltaic cells

Main article: Solar cell

The Shockley–Queisser limit gives the maximum possible efficiency of a single-junction solar cell under un-concentrated sunlight, as a function of the semiconductor band gap. If the band gap is too high, most daylight photons cannot be absorbed; if it is too low, then most photons have much more energy than necessary to excite electrons across the band gap, and the rest is wasted. The semiconductors commonly used in commercial solar cells have band gaps near the peak of this curve, as it occurs in silicon-based cells. The Shockley–Queisser limit has been exceeded experimentally by combining materials with different band gap energies to make, for example, tandem solar cells.

The optical band gap (see below) determines what portion of the solar spectrum a photovoltaic cell absorbs. Strictly, a semiconductor will not absorb photons of energy less than the band gap; whereas most of the photons with energies exceeding the band gap will generate heat. Neither of them contribute to the efficiency of a solar cell. One way to circumvent this problem is based on the so-called photon management concept, in which case the solar spectrum is modified to match the absorption profile of the solar cell.

List of band gaps

Below are band gap values for some selected materials. For a comprehensive list of band gaps in semiconductors, see List of semiconductor materials.

Group	Material	Symbol	Band gap (eV) @ 302K
III–V	Aluminium nitride	AlN	6.0
IV	Diamond	C	5.5
IV	Silicon	Si	1.14
IV	Germanium	Ge	0.67
III–V	Gallium nitride	GaN	3.4
III–V	Gallium phosphide	GaP	2.26
III–V	Gallium arsenide	GaAs	1.43
IV–V	Silicon nitride	Si3N4	5
IV–VI	Lead(II) sulfide	PbS	0.37
IV–VI	Silicon dioxide	SiO2	9
	Copper(I) oxide	Cu2O	2.1

Optical versus electronic bandgap

In materials with a large exciton binding energy, it is possible for a photon to have just barely enough energy to create an exciton (bound electron–hole pair), but not enough energy to separate the electron and hole (which are electrically attracted to each other). In this situation, there is a distinction between "optical band gap" and "electronic band gap" (or "transport gap"). The optical bandgap is the threshold for photons to be absorbed, while the transport gap is the threshold for creating an electron–hole pair that is not bound together. The optical bandgap is at lower energy than the transport gap.

In almost all inorganic semiconductors, such as silicon, gallium arsenide, etc., there is very little interaction between electrons and holes (very small exciton binding energy), and therefore the optical and electronic bandgap are essentially identical, and the distinction between them is ignored. However, in some systems, including organic semiconductors and single-walled carbon nanotubes, the distinction may be significant.

Band gaps for other quasi-particles

In photonics, band gaps or stop bands are ranges of photon frequencies where, if tunneling effects are neglected, no photons can be transmitted through a material. A material exhibiting this behaviour is known as a photonic crystal. The concept of hyperuniformity has broadened the range of photonic band gap materials, beyond photonic crystals. By applying the technique in supersymmetric quantum mechanics, a new class of optical disordered materials has been suggested, which support band gaps perfectly equivalent to those of crystals or quasicrystals.

Similar physics applies to phonons in a phononic crystal.

Materials

• Aluminium gallium arsenide
• Boron nitride
• Indium gallium arsenide
• Indium arsenide
• Gallium arsenide
• Gallium nitride
• Germanium
• Metallic hydrogen

List of electronics topics

• Electronics
• Bandgap voltage reference
• Condensed matter physics
• Direct and indirect bandgaps
• Electrical conduction
• Electron hole
• Field-effect transistor
• Light-emitting diode
• Photodiode
• Photoresistor
• Photovoltaics
• Solar cell
• Solid state physics
• Semiconductor
• Semiconductor devices
• Strongly correlated material
• Valence band