Assuming that the RC time constant of the low-pass filter is long enough to smooth out the PWM ripple, is the relationship between output voltage and duty cycle a linear percentage of the voltage based on the percentage of the duty cycle? Martin McCormick WB5AGZ Stillwater, OK OSU Information Technology Division Network Operations Group -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu