Hi Werner What frequency are you working at? Most PCB coil calculations work in impedance terms as in ohms / mm when = at RF frequencies. You then just have to zigzag the track to fit into the space you're = using. Below RF you have to use conventional components. Cheers Mark ------------------------------------------------------------------- Mark Hull Engineering/Technical EMS (Africa) (Pty) Ltd PO Box 1026, Melville, 2109, South Africa Ph +27 11 482 4470 Fax +27 11 726 2552 -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.