OL> Dumitru Stama wrote:
>> I attached the updated schematics.

OL> So you made it AC coupled and increased the input impedence.  That's better,
OL> but there are still problems.

OL> 1 - There should be a cap to ground from the node between R1 and R2.
OL> Otherwise any supply noise and anything that node picks up is going to end
OL> up on the signal.  There should be at least a 100nF ceramic, and maybe a
OL> 10uF electrolytic too.  A single 1uF ceramic is probably good enough.

I will fix this and post the new schematics again. I forgot about the
noise.

OL> 2 - You didn't look up the supply requirements of the TL072 like I said to,
OL> did you?  I can't get the TI web site right now for some reason, but I'm
OL> pretty sure 5V isn't enough.  You have also ignored what I said about supply
OL> headroom.

I think i overlooked this part but not by mistake but because i
thought 2v headroom means 2v between + and -. My english is playing
tricks on me. I will try with 9v to be sure and i will post some
images with the scope and self-oscilations if any.
Thank you for your help

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