It doesn't matter if National is #1 or #37; here at Wikipedia, the linkspam policy clearly discourages the posting of commercial links on a "generic" page like the voltage regulator page. Sometimes, if the list of manufacturers isn't long, it's accepted if all of the relevant players are linked, but there are just too many vendors of VR chips, bricks, etc.

I believe it is entirely reasonable to remove the NatSemi link.