Integrating op amp question

  • #1
Hello,
I'm having problem understanding the output of the integrating op amp.

https://www.dropbox.com/s/djpg0uhi465ot86/download2.png
https://www.dropbox.com/s/djpg0uhi465ot86/download2.png

https://www.dropbox.com/s/p9bp9tlyykhjtvf/download.png
https://www.dropbox.com/s/p9bp9tlyykhjtvf/download.png
(hope you can see that, I can't see it on my preview)

The blue line is input, orange is output. So if it's supposed to integrate, surely output signal has a wrong sign, doesn't it? If the integral is the area under the square signal, there should be linear increase when the signal is positive and linear decrease when it's negative, yet it's the other way around, why? I'd thought it was because my voltage had been applied to the inverting input of the op-amp, but even when I flipped it, it stays the same...
 
Last edited:

Answers and Replies

  • #2
jim hardy
Science Advisor
Gold Member
Dearly Missed
9,839
4,881
Remember you have an inverting amplifier there.
The opamp will hold its inputs equal, and +input is at zero.
Therefore whatever current is pushed into summing junction through R1 must get pulled back out through C1&R2,,,,
,,,so an input to output reversal of polarity is nessary.

After the initial transient (power up i presume?) , output looks like it moves in right direction.

http://www.ti.com/ww/en/bobpease/assets/AN-31.pdf
 
Last edited:

Related Threads on Integrating op amp question

Replies
13
Views
6K
  • Last Post
Replies
15
Views
3K
  • Last Post
Replies
3
Views
6K
  • Last Post
Replies
3
Views
4K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
22
Views
3K
  • Last Post
Replies
13
Views
3K
  • Last Post
Replies
6
Views
3K
  • Last Post
Replies
13
Views
4K
  • Last Post
Replies
7
Views
2K
Top