Electronic – OpAmps – Single Supply or Dual

datasheetoperational-amplifierpower supply

I'm trying to pick an op-amp and I'm having trouble figuring out if the op-amp needs a positive and a negative power supply or if I can connect it to ground and the positive supply.

What do I need to look for in the datasheet?

Also, where do I find the "drop-out" of the output compared to the rail voltage?

Best Answer

Most if not all op-amps can be used in either configuration. Voltage is relative, and "ground" is just an arbitrary potential that you assign the value of 0 volts. There are op-amps "optimized" for one configuration or the other, but they can be used in either. This op-amp, for instance, is "optimized for single supply operation", and they emphasize features like:

  • Input Voltage Range Extends to Ground
  • Output Swings to Ground while Sinking Current

but "Specifications at ±15V are also provided."

Op-amps meant for single-supply often have rail-to-rail outputs, which will usually be featured on the front page of the datasheet. To find the "drop-out", look for a graph like "Maximum Output Voltage Swing vs Load Resistance" in this datasheet.

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).

A Single Supply Op Amp Circuit Collection