Hi all,

I have to drive the binary inputs 4067 (analog mux) with the micro 2051.

Micro is at 5 volts and 4067 is at 12 volts.

As far as I keep the supply for both at 5 volts from the same rail, 4067 runs fine.

However, for some necessary reasons, when I run 4067 at 12 volts (the same source voltage is used with 7805 and 7812), 4067 does not run.

Do I need some kind of isolation between 3051 and 4067. I tried simple npn driven form micro giving ground out to 4067 and pulled 4067 inputs high with 10K to 12 volts. And kept the micro out pulled high with 10K to 5 volts.

I also tried 4050 (hex buffer) at 12 volts with micro at 5 volts. Didn't work either.

Any help is appreciated please.

Babar