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I'm using the 741 op-amp and I want to check its open-loop gain. The model specifications in Multisim show that A = 200000 for this op-amp.

This is the circuit I am using:

enter image description here

The output I am getting is a bit strange to me. With an input signal of 1 Hz and 1 V amplitude, I am getting a square wave, like so, with an amplitude of 11.18 V: (cyan represents input signal, and red represents output signal)

enter image description here

I supposed that this is a result of clipping, as $$V_o = A\times V_{in} = 200000\times V_{in}$$ which does exceed 12 V by a lot. So I tried with an input of 25 μV, as then $$V_o=200000\times 25 \times 10^{-6}=5\ \mathrm{V}$$

But then, this is my output: (now a straight line at 11.115 V)

enter image description here

From my understanding, it should have been a sine wave with 5 V amplitude. What is going wrong here?

ocrdu
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Techie5879
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    I don't think that's a good way to measure open loop gain on a real opamp. It might only work out for ideal models. Looks to me like the input offset voltage is swamping out your input signal, causing the saturation to stick to the positive rail. This question recently addressed better ways to do this; it uses an AC analysis which linearizes the circuit and avoids the saturation problem due to non-idealities: https://electronics.stackexchange.com/questions/640240/what-is-the-best-way-to-simulate-the-open-loop-gain-of-an-op-amp-in-ltspice – Ste Kulov Nov 02 '22 at 06:43

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