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The open loop gain of an ideal opamp is “infinite', in practice it’s somewhere between 100,000V/V to 1,000,000 V/Vand up. Ideally that would mean a very small voltage swing between the inputs would cause the output to be in the hundreds of thousands of volts, but practically the output is limited by the maximum and minimum values dictated by the supply rail voltages(This is known as saturation, this is how Comparators are used, will discuss more later).
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