Open Loop Gain

I assume you're asking for a reason, and we could probably give a better answer if we knew the reason.

But, I'll make an attempt. An op amp is an (operational) amplifier. It will allow you to input a signal of a given level and get a signal of a higher level out. The ratio of the output signal to the input signal is the gain. I think it is most often a voltage gain, but it could also be a current gain.

In an amplifier you can have a feedback loop, whereby part of the output is fed back to the input. In general, this is done to increase the stability of the amplifier. If the amplifier is unstable, you can get effects like oscillation or distortion.

When a feedback loop is present, the gain measured then is called closed loop gain.

When a feedback loop is not present, the gain measured is called open loop gain.

You should try looking some of these terms up on the Internet, using google. I'll bet Wikipedia, has a pretty good article on op amps, open loop gain, closed loop gain, and similar. I'll bet you can find some good answers with pictures and such.

Click this link!

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There is also some key things that the open loop gain of an op-amp tells a circuit designer. The easiest thing that one realizes is that since an op-amp does actually have a finite gain, the first order calculations and rules of thumb of amplifier gain are not precisely correct. For example, in the inverting amplifier configuration there are actual signal voltages on the inverting node of the op-amp. They are very tiny voltages but they are still there. This virtual ground node will not really be at ground potential.

This parameter is but one of many real versus ideal parameters one should understand of an op-amp.

about 100,000