I use Arduino DUE to generate a 100 Hz pulse.
I wanted to remove the DC value so I added a high pass filter and this is connected to the Op Amp(ADA4000-1)'s input. A RIGOL's DP832 power supply is giving +/- 9V to the Op Amp.
These are connected to the breadboard and I noticed when I change R2's value.
The following screenshots are the Op Amp's output.
- R2 = 0 (Unity gain)
Some noise is discovered from the signal's positive peak.
- R2 = 40k, gain = 5
When the gain becomes bigger, reversely, the signal's negative peak shows noise and the flat line after the positive peak seems noisy.
- What seems to be the reason for the noise when the gain changes?
- Also, what could be the solution to remove these noises?
EDITED: You guys are right; the output was unstable due to the missing decoupling caps.
I changed it to a unity gain buffer.
Before adding the decoupling capacitor to the negative terminal,
the same phenomenon was shown.
As you see my pen pointing, adding 100nF cap, now it is giving a stable output! Thanks!
Two more things;
When I touch the Op Amp's output with my finger, I discovered that the output becomes stable (by looking at the oscilloscope) without the decoupling capacitor. Why did this happen?
This happened due to the unpopulated decoupling capacitor. Is there a name/technical jargon of this phenomenon?