The positive and negative ends of the op amp are not equal

jiyu75

The positive and negative ends of the op amp are not equal [Copy link]

The attached is my circuit. I hope to compare the DC voltage difference between point A and point B, that is, to make a subtractor, and then amplify the output, but I don't know why the output is wrong. The actual test results are in the attached picture. Can someone analyze what's going on?

maychang

Then amplify the output, but for some reason the output is not right. Your op amp is not connected for amplification, the output is connected to the in-phase input via R13.

jiyu75

maychang posted on 2018-8-2 15:16 Then amplify the output, but I don't know what's going on, the output is wrong. Your op amp is not connected for amplification, the output end is connected through R13...

I don't understand, can you explain it in more detail? What do you suggest to change?

wsmysyn

Your amplifier is connected wrongly. The in-phase and inverting terminals are reversed.

jiyu75

Got it, thank you two heroes

maychang

jiyu75 posted on 2018-8-2 15:43 I don't understand, can you explain it in more detail? What do you suggest to change?

See the reply on the 4th floor. He said it simply.

chenbingjy

Should it be connected to the feedback input terminal?

elvike

To connect to negative feedback