In this standard inverting amplifier configuration, you can vary the
op amp's open-loop gain continuously with the slider on the right.

Note that as you make the open-loop gain larger and larger, the differential input voltage V_{diff} and the differential input current I_{d} get smaller and smaller. Also, the actual closed-look gain becomes closer and closer to the nominal gain given by the
ratio of R_{2} to R_{1}. Real operational amplifiers have
open loop gains that are so high (50,000 or more) that is a good approximation to
assume that it is infinite, and therefore that the differential input voltage V_{diff} and the differential input current I_{d} are both zero. This is not exactly true,
of course, but the accuracty of this approximation is better that the accuracy of the
resistors (even of precision resistors).

In this simulation you can change the values of R_{1}, R_{2} and the differential input resistance (typically 1 to 100 Megohm).

This page is maintained by Prof. T. C. O'Haver , Department of Chemistry and
Biochemistry, The University of Maryland at College Park.
Comments, suggestions and questions should be directed to
Prof. O'Haver at toh@umd.edu.
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