I built a Multiple Feedback low pass filter on the breadboard using an LM7171. Below is the schematics:
While doing measurements, I noticed two things:
- Large DC bias at the input R3 and the output of the op amp.
- The signal at the output is severely attenuated even at low frequencies.
I ran a frequency response analysis and below are the results obtained:
The response is not for a low pass filter. The gain of the signal seems to increase as frequency go up.
Any Idea on what I'm doing wrong?