> Remember that in the real world a constant current source may fail at 5V or 100V ( or whatever ). This happens when the capacitor voltage gets near the constant current's supply voltage. So model the current source at something much larger (100kV) and a series resistor that limits the current to 10mA. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .