>> as shown this circuit has a major problem. > This is a problem only with your altered version. True. I missed the overall result of the current source, which is obvious enough in retrospect. The ability to thereby set the maximum high side drive voltage is quite useful. Russell McMahon -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist