Open-loop gain: Difference between revisions

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{{Unreferenced stub|auto=yes|date=December 2009}}

The '''open-loop gain''' of an [[operational amplifier]] is the [[gain]] obtained when no [[feedback]] is used in the [[electrical network|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 ana maximal 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 theThe very high open-loop gain of the op-amp enablesallows considerablea levelswide range of feedback levels to be applied to achieve requiredthe desired 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]].

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>

The definition of open-loop gain (at a fixed frequency) is

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.

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

where <math>V^+-V^-</math> is the input voltage difference that is being amplified. The dependence on frequency is not displayed here.

== See also ==