analog filter stability ideas

[phil2014]

Hi all,

I have the following LTSpice low pass filter circuit simulation and resultant ac analysis (full ltspice project is attached).  The problem is that the first filter stage oscillates in my test PCB - even without load (delete R1).  The second stage is stable.

I am looking for ideas on how to improve circuit stability and am hoping someone with more experience can guide me in the right direction.





Regards

[R_G_B_]

This is useful to watch on amplifier stability:



R_G_B

[phil2014]

Thanks.  For the link.  After reading up a bit more I decided to increase the phase margin by reducing band pass ripple.  The circuit no longer resonates 

[diyaudio]

This is useful to watch on amplifier stability:



R_G_B