# Open-loop gain

The open-loop gain of an operational amplifier is the gain obtained when no feedback is used in the circuit. Open loop gain is usually exceedingly high; in fact, an ideal operational amplifier has infinite open-loop gain. Typically an op-amp may have a maximal open-loop gain of around $10^5$. Normally, feedback is applied around the op-amp so that the gain of the overall circuit is defined and kept to a figure which is more usable. The very high open-loop gain of the op-amp allows a wide range of feedback levels to be applied to achieve the desired performance.
$A_{\text{OL}}=\frac{V_{\text{out}}}{\left(V^+-V^-\right)},$
where $V^+-V^-$ is the input voltage difference that is being amplified. The dependence on frequency is not displayed here.