I asked son M this morning to search for an integrated circuit for me. The last time I checked, they were out of stock in town. I need it for what I call my last big design. I am (almost) as far as having all the components together on a tray (pictured). It is a magnetometer, to detect variations in magnetic field strength. The plan is to build two five-stage amplifiers, to detect variations in magnetic field strength (successfully tested), then to feed these to a comparator out of phase (not tested). In this way, one cancels out variations affecting both channels but not one -- such as the earth's magnetic field. The tested sections are immensely sensitive.