>Well, my (20 years old) RCA CMOS Databook says 20V as absolute maximum supply >voltage for all 4000-series chips. Has that been changed? All my books say 15V, 18V for the B series. And if the input exceeds the supply voltage, it'll latch-up. I assume that to be absolutely safe you'd have to clamp the inputs. Terry Bowman, KA4HJH "The Mac Doctor"