All op amps have two power pins. In most cases, they are labeled VCC+ and VCC-, but sometimes they are labeled VCC and GND. This is an attempt on the part of the data sheet author to categorize the part as a split-supply or single-supply part. However, it does not mean that the op amp has to be operated that way— it may or may not be able to operate from different voltage rails. Consult the data sheet for the op amp, especially the absolute maximum ratings and voltage-swing specifications, before operating at anything other than the recommended power-supply voltage(s).
Most analog designers know how to use op amps with a split power supply. As shown in the left half of Figure 1, a split power supply consists of a positive supply and an equal and opposite negative supply. The most common values are ±15 V, but ±12 V and ±5 V are also used. The input and output voltages are referenced to ground, and swing both positive and negative to a limit of VOM±, the maximum peak-output voltage swing. A single-supply circuit (right side of Figure 1) connects the op-amp power pins to a positive voltage and ground. The positive voltage is connected to VCC+, and ground is connected to VCCor GND. A virtual ground, halfway between the positive supply voltage and ground, is the reference for the input and output voltages.
The voltage swings above and below this virtual ground to the limit of VOM±. Some newer op amps have different high- and low-voltage rails, which are specified in data sheets as VOH and VOL, respectively. It is important to note that there are very few cases when the designer has the liberty to reference the input and output to the virtual ground. In most cases, the input and output will be referenced to system ground, and the designer must use decoupling capacitors to isolate the dc potential of the virtual ground from the input and output. See this picture:
