Operational amplifier stability analysis problem

呜呼哀哉

Operational amplifier stability analysis problem [Copy link]

As shown in the following figure, please give me some advice.

呜呼哀哉

Hold it up yourself and don't let it sink.

The result should be 2 is correct, but I don't know why 1 is wrong.

gmchen

The picture is crooked. It can treat cervical spondylosis, but it is too tiring.

In result 1, you confused β with 1/β. The first part, the ratio of the two resistors, was plotted with the inverse, which is correct. The second part, the zero and the pole, was plotted without the inverse, which is wrong.

呜呼哀哉

gmchen published on 2021-4-27 08:51 The picture is crooked, it can treat cervical spondylosis, but it is too tiring. In result 1, you confused β with 1/β. The ratio of the two resistors in the first part...

You are right. That's great. The β written in equation 1 does have the numerator and denominator reversed, which results in the wrong order of the poles and zeros.

Thank you so much. I must change my careless habit.

gmchen

Being able to write this transfer function and correctly draw the Bode plot of the op amp open-loop function shows that you have learned well! It is worth encouraging!