IC power-supply pin

185px|thumb|Power-supply inputs on circuit boards with screen-printed voltage subscripts

IC power-supply pins are voltage and current supply terminals found on integrated circuits (ICs) in electrical engineering, electronic engineering, and integrated circuit design. 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 double-subscript notation usually corresponds to a first letter in a given IC family (transistors) notation of the terminals (e.g. V_DD supply for a drain terminal in FETs etc.).

{| class="wikitable"

|+ Typical supply-pin labeling

!

! NPN BJT

! N-FET !! !!

!

!DC

!DC

|-

| Positive supply voltage || V_CC/V_BB || V_DD || V+ || V_S+

|VIN

|VDD

|

|-

| Negative supply voltage || V_EE || V_SS || V− || V_S−

|

|

|

|-

| Ground || GND || GND || 0 || 0

|GND

|GND

|GND

|}

The simplest labels are V+<!--unfortunately this one can't be redirected here currently--> 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.

For power supplies, sometimes one of the supply rails is referred to as ground (abbreviated "GND") positive and negative voltages are relative to the ground. In digital electronics, negative voltages are seldom present, and the ground nearly always is the lowest voltage level. In analog electronics (e.g. an audio power amplifier) the ground can be a voltage level between the most positive and most negative voltage level.

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).<!-- Both these references are dead links feb. 2, 2017 -->

BJTs

ICs using bipolar junction transistors have V_CC (+, positive) and V_EE (-, negative) power-supply pins though V_CC is also often used for CMOS devices as well.

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 R_C, R_E, and R_B. In order to create the DC voltages, the furthest voltage, beyond these resistors or other components if present, was often referred to as V_CC, V_EE, and V_BB. In practice V_CC and V_EE then refer to the positive and negative supply lines respectively in common NPN circuits. Note that V_CC would be negative, and V_EE would be positive in equivalent PNP circuits.

The V_BB specifies reference bias supply voltage in ECL logic.

FETs

Exactly analogous conventions were applied to field-effect transistors with their drain, source and gate terminals.