@Olin, note: in this circuit ( http://www.eng.utah.edu/~jnguyen/ecg/bigsch.gif), they seem to have made their own instrumentation amplifier that looks like this http://www.allaboutcircuits.com/vol_3/chpt_8/10.html. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .