modified 9 years ago

OpAmp - circuit without and with negative feedback

00:19:00

In this circuit the first there is no negative feedback in the first OpAmp, then we cannot assume that "Vp = Vn" (this is valid only when there is negative Feedback).

But there is negative feedback in the second OpAmp.

We can write the KCL equation for Vn1 and the equation for the output of OpAmp 1 based in the general equation "A(Vp - Vn)".

The output of OpAmp 1 is applied in the second OpAmp, an inverting configuration. Based in this is possible to write the output equation to this second OpAmp.

Now it's possible to write the KCL for the node Vp1. Even without the negative feedback, the voltage at both inputs in OpAmp 1 is equal, that is, it's not saturating.

With Vp1 it's possible to calculate the currents and to know the voltage of OpAmp 1.

Circuit explanation by professor L.R. Linares: https://www.youtube.com/watch?v=dkTjbcSEHmc

published 9 years ago

jewel2020

9 years ago

Why don't you check this? https://www.youtube.com/watch?v=Xh0w50XqUNg

agaelema

9 years ago

@jewel2020, I watched this video today, before post the circuit. But I think that the explanation using de complete analysis is more secure, because the negative feedback is no explicit, the second OpAmp change the polarity of the voltage.

agaelema

9 years ago

But I follow the videos of EE Academy and like a lot.

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