> The comparators are feeded at the voltage provided as 12V > 13.8V unrectified may power some sensors ? Isn't this dangerous > for them ? Can you tell us what the comparators and sensors are please, if that's possible. I'm sure there's a circuit, probably using other parts than those you're designing with now, that can be suggested for your needs, and it's a good bet that the voltages required won't need to be as rigid as you might think -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.