IC power supply pins
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)
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 VC , VE , and VB , 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.
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