Open-loop gain: Difference between revisions

Content deleted Content added

Inline

Revision as of 19:26, 20 March 2014

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.

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.

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

$A_{\text{OL}}={\frac {V_{\text{out}}}{\left(V^{+}-V^{-}\right)}},$

where $V^{+}-V^{-}$ is the input voltage difference that is being amplified. The dependence on frequency is not displayed here.

@@ Line 1: / Line 1: @@
 {{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 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]].
+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 <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. 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.
+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 ==