Wagner Lipnharski wrote: > Integrate the square wave in two capacitors, using two resistors, one > for each capacitor in a traditional R+C configuration. ... et al. In short, use a current driver to convert it to a precision triangle wave, low-pass filter it (or use a "slicer") to obtain the mid-point and compare the two to derive your 90¡ shift. Very elegant Wagner! -- Cheers, Paul B.