By Erin Coe

Law360, New York (September 28, 2007, 12:00 AM ET) -- Alpha & Omega Semiconductor Inc. and larger rival Fairchild Semiconductor Corp. have expanded their patent infringement and declaratory judgment cases against one another over metal-oxide-semiconductor field-effect, or MOSFET, products.

AOS filed its first amended complaint Friday in the U.S. District Court for the Northern District of California and accused Fairchild of willfully infringing three of its patents related to its power transistor products and asserting that Fairchild’s four patents were invalid and not infringed.

In its initial complaint, filed on May 17, AOS claimed that Fairchild...