Would there be a problem using an internal comparator on the PIC for the rectifier op amp? I did this for an S meter for a tracking receiver monitor.I used a germanium diode in series with the feedback resistor. As I understand it, before the diode conducts, the op amp gain is very high. After it forward conducts, the op amp gain becomes the ratio between the two gain setting resistors, effectively reducing the diode voltage loss to a very low value. Even though the comparators are not meant for high frequency work, the circuit worked quite well.But...What if the AC voltage goes below Vss?

Ron