Hi Fred, Either way can work if done properly. I've gone back and forth on this philosophy. It is much like shielding. Many people think that they can just "throw" a technique at a project and fix their problems. Just putting a messily-radiating device inside of a shielded box rarely fixes the problem, yet there are cases where shielding is an indispensable part of the RFI solution. Similarly, just putting analog and digital grounds on two separate planes without thinking through the implications of that is likely to cause more problems than it solves. My overall guess would be that it would be better to use a single ground plane. If you use a differential input as I suggested, that should help to prevent picking up differences in ground potential as signals. Sean On Sun, Jul 27, 2008 at 8:17 PM, fred jones wrote: > > Thanks Sean, > I really appreciate all your help. Could you comment on PCB layout for me? Should I create one ground plane or should I take the digital sections and place them on their own plane and put the amplifiers on their own ground plane? Again, thanks so much for taking the time to offer advice. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist