Ok, thanks, guys. I read very carefully datasheets and compare the charts, and Kai is right for me too. It seems it's not only the board. I achieve the needed resolution with ADuC824 with an external amplifier, but that's not the solution, cause the temperature stabillity is also important for me and is pointless to use ADuC in this kind of schematic. And i need at least 100 000 stable divisions. So, i will use again AD7730 in AC mode. Thank you