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Almost all integrated circuits (ICs) have at least two pins that connect to the power rails of the circuit in which they are installed. These are known as the power-supply pins. However, the labeling of the pins varies by IC family and manufacturer. The simplest labels are V+ and V−, but internal design and historical traditions have led to a variety of other labels being used. V+ and V− may also refer to the non-inverting (+) and inverting (−) voltage inputs of ICs like op amps. Sometimes one of the power-supply pins will be referred to as ground (abbreviated "GND"). In digital logic, this is nearly always the negative pin; in analog integrated circuits, it is most likely to be a pin intermediate in voltage between the most positive and most negative pins . While double subscript notation, where subscripted letters denote the difference between two points, uses similar looking placeholders with subscripts, the double letter supply voltage subscript notation is not directly linked (though it may have been an influencing factor)〔(Micro E, 7. Integrated circuits )〕〔(Washington and Lee University, Lexington, VA, Op-amps: Some Standard Conconfigurations and Applications, Fall 2012 )〕 == History == In circuit diagrams and circuit analysis, there are long-standing conventions regarding the naming of voltages, currents and some components. In the analysis of a bipolar junction transistor, for example in a common emitter configuration, the DC voltage at the collector, emitter, and base (with respect to ground) may be written as ''V''C, ''V''E and ''V''B respectively. Resistors associated with these transistor terminals may be designated ''RC'', ''RE'' and ''RB''. In order to create the DC voltages, the furthest voltage, beyond these resistors or other components if present, was often referred to as ''VCC'', ''VEE'' and ''VBB''. In practice ''VCC'' and ''VEE'' then refer to the plus and minus supply lines respectively in common NPN circuits. Note that ''VCC'' would be negative and ''VEE'' would be positive in equivalent PNP circuits. Exactly analogous conventions were applied to field-effect transistors with their drain, source and gate terminals.〔 This led to ''VD'' and ''VS'' being created by supply voltages designated ''VDD'' and ''VSS'' in the more common circuit configurations. In equivalence to the difference between NPN and PNP bipolars, ''VDD'' is positive with regard to ''VSS'' in the case of ''n''-channel FETs and MOSFETs and negative for circuits based on ''p''-channel FETs and MOSFETs. Although still in relatively common use, there is limited relevance of these device-specific power supply designations in circuits that use a mixture of bipolar and FET elements, or in those that employ either both NPN and PNP transistors or both ''n''- and ''p''-channel FETs. This latter case is very common in modern chips, which are often based on CMOS technology, where the ''C'' stands for ''complementary'' meaning that complementary pairs of ''n''- and ''p''-channel devices are common throughout. These naming conventions were part of a bigger picture where, to continue with bipolar transistor examples although the FET remains entirely analogous, DC or bias currents into or out of each terminal may be written ''IC'', ''IE'' and ''IB''. Apart from DC or bias conditions, many transistor circuits also process a smaller audio-, video- or radio-frequency signal that is superimposed on the bias at the terminals. Lower case letters and subscripts are used to refer to these signal levels at the terminals, either peak-to-peak or rms as required. So we see ''vc'', ''ve'' and ''vb'' as well as ''ic'', ''ie'' and ''ib''. Using these conventions, in a common emitter amplifier, the ratio ''vc''/''vb'' represents the small-signal voltage gain at the transistor and ''vc''/''ib'' the small-signal ''trans-resistance'' from which the name ''transistor'' is derived by contraction. In this convention, ''vi'' and ''vo'' usually refer to the external input and output voltages of the circuit or stage.〔 Similar conventions were applied to circuits involving vacuum tubes or ''thermionic valves'' as they were known outside of the U.S. Therefore, we see ''VP'', ''VK'' and ''VG'' referring to plate (or ''anode'' outside of the U.S.), cathode (note ''K'', not ''C'') and grid voltages in analyses of vacuum triode, tetrode and pentode circuits.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「IC power-supply pin」の詳細全文を読む スポンサード リンク
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