Open-loop gain: Difference between revisions

Revision as of 13:55, 26 September 2011

Revision as of 13:38, 20 February 2012

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Open loop gain is usually exceedingly high; in fact, an ideal operational amplifier has infinite open-loop gain. Typically an op-amp may have an open-loop gain of around <math>10^5</math>. Normally, feedback is applied around the op-amp so that the gain of the overall [[electrical network|circuit]] is defined and kept to a figure which is more usable. However the very high gain of the op-amp enables considerable levels of feedback to be applied to achieve required performance. The open-loop gain of an operational amplifier falls very rapidly with increasing [[frequency]]. Along with [[slew rate]], this is one of the reasons why operational amplifiers have limited [[Bandwidth (signal processing)|bandwidth]].

<math>A_{\text{OL}}=\frac{V_{\text{out}}}{\left(V^+--V^-+\right)}</math>

As you can see from the definition above, in an ideal amplifier where <math>V^+=V^-</math>, the open loop gain (<math>A_{\text{OL}}</math>) becomes infinite.