Hi Neil, On 13 April 2012 00:26, Neil wrote: > What exactly do you mean by "clamping the output"? =A0I actually need 0.5= V > to 4.5V output, and Vdd will be 5V. =A0But I was looking for the A/D > feedback,etc for accuracy, since the PWM voltage output will be subject > to variations in Vdd. > > Cheers, > -Neil. > Basically I was thinking about a system where the output voltage was limited to, say, 4.5V by means of a series resistor & precision zener / TL431 etc. This would then be independent of supply voltage but subject to any temperature drift in the clamping device. The minimum voltage would be close to zero - if you need it to be 0.5V, then you'd need to add it in - use an opamp circuit to provide the clamping function with a 0.5V offset.? RP --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .