hi steve
what about LM318 , for analog signal aplification , charging time 10us then lap about 30us for discharging for high voltege then measur charg on inductor , here are 2 coils one for charging only, and the other one is for senceing metals , the discharging time goes change if there will be any metal, im making sensitve metal detector that must be able to detect less than 0.5gram /grains , range is not suche important , if u have worked on this type of projects , pls help me , stability/sensitivity must be good enough , whats about the code for filteration (band pass) , i hope you will help

regards

fk