i am working on dc-dc converters and want to simulate on spice or cadence.
can you please tell me which library is used in spice.and which version of spice is used.
I think you're going to suffer, unless you get into behavioral modeling.
Linear Tech's LTCSpice (I think it may have recently gotten
a new "stage name", but it's still free for download) has been
modified to do a better job with switching power supply
type circuits, and has a lot of part types modeled for you. I'd
check that out first. Schematic capture, too.