An operational amplifier outputs the difference between its two inputs multiplied by a fixed constant gain, regardless of the input signal conditions.

An ideal operational amplifier produces an output that equals the difference between its two input voltages multiplied by its open‑loop gain, so the basic relationship is \(V_{out}=A_{ol}(V_{+}-V_{-})\). In practice, the gain is finite and the amplifier has limits such as supply voltage, input bias current, offset voltage, bandwidth, and slew‑rate, so the output may saturate or distort at high frequencies or large input differences. For example, if a 10‑gain op‑amp has \(V_{+}=1. 0\text{ V}\) and \(V_{-}=0. 5\text{ V}\), the ideal output would be \(5\text{ V}\), but if the supply rails are ±5 V the amplifier will clamp at the rails and the real output might be slightly lower.