Explain the need for a dual power supply in opamp.

Subject: Liner Integrated Circuits

Topic: Introduction to operational amplifiers

Difficulty: Low

1 Answer

Need for a dual power supply in OPAMP

Operational amplifiers have two power supply rails because they usually need to swing bipolar - output voltages that go either positive or negative in response to the normal range of input signals. Usually the signals in an operational amplifier are relative to a ground that is somewhere between the two rails, thus the plus supply and minus supply are usually, but not always, symmetrical about ground.

Without the dual supplies the output signal would clip at the ground potential.


If you look at a pinout connection diagram for a standard opamp you will notice there is no ground terminal pin at all. Thus the opamp only needs the voltage between the positive rail and the negative rail to work which could be supplied by a single power supply equal to the sum. But usually circuits usually need a ground reference and so the opamps are described as having two power supplies.

If you don't have or need a ground reference the opamp can be supplied with a single supply no greater than the sum of the two supplies. Historically though, op amp suppliers have listed supplies of +/-15 V or +/-5 V and not 30 V and 10 V respectively.

Please log in to add an answer.