After some time when AD8436 RMS to DC was working fine in configuration without input buffer and with simple follower with no gain on output buffer, I received new packet of AD8436s an result was shocking - there is huge ripple on output buffer - on input into this buffer there is no noise. I tested same design on two boards and both have this problem.
From the scope pictures in attachment you can see what is happening from input to RMS, through output from RMS to output of OutputBuff.
Design is simple as it can be:
Thank you for support and best regards,