When Paulina Sliwinska, a fund manager at Edinburgh-based Baillie Gifford & Co., made the trip to Silicon Valley looking for the next big thing in technology, she found it -- not in a hot startup run by a 23-year-old whiz kid just out of Stanford, but in a 23-year-old semiconductor maker that's had the same chief executive officer since its founding. Jen-Hsun Huang, CEO of graphics-chip maker Nvidia Corp., has won over Sliwinska and many other investors this year with claims that his products, once confined to the niche of computer-gaming machines, are breaking out to become key components of nascent technologies from voice recognition to self-driving cars.