Hi, I am working on project that encompasses picking up surface potentials on the forearm which are then passed through an instrumentation amplifier (gain=10), passive high-pass filter (fc=15 Hz), gain stage (gain=100), and finally a precision rectifier with a capacitor in parallel with the feedback resistor R5 to create a low-pass filter (fc=800). Upon hooking everything up things seem to work normally except for the output of the rectifier. I am getting a high-frequency oscillation (50-100 KHz). Trying to deduce the problem I ran through my simulations again but found that they were showing a phase margin of around -71deg which is more than enough room. I am seeing this when I am using both a battery supply and a wall-wart. Attached are my schematic and frequency response. Wondering if anyone has any suggestions. I've been at this for a while now, can't seem to crack the code.