Byron Jeff mail.clayton.edu> writes: > > Dave Tweed wrote: > > Use a transistor already! > > Actually I did that and it changed the timing on the pin. When I changed > out the signal diode with a zener, the timing reverted back to its normal > behavior. Miller effect says hello. The transistor used for this needs to be very sma= ll Ccb, usually a rf type. The clamp I proposed (years ago) and linked in this thread, does not have this problem as it is a common base circuit (very fas= t too). TAINTSTAAFL. I wonder how long it will take for the semiconductor mak= ers to start implementing CMOS active clamps in the input pin internal silicon structures proper. Microchip certainly has stringent body diode leakage requirements which other makers (Atmel) do not have. Atmel mcu's have 10 bi= t adcs and do not exhibit anything anywhere near the problems seen with Micro= chip body diode currents. I admit to be a defector to the Atmel side for now :) -- Peter --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .