Mar Hershenson came to Silicon Valley from Barcelona, Spain, for a summer job, met her future husband and stayed, bringing a bit of her native city to California in the form of Barcelona Design, which she cofounded in 1999.The Sunnyvale, CA, company produces software and intellectual property, developed by Hershenson, for quickly optimizing the design of analog circuits for cell phones, TVs and DVD players. Previously, engineers could spend a year designing a single analog chip. With Barcelona’s solution, custom analog circuits can be finished in hours. Hershenson’s breakthrough was to represent circuits with equations that can be solved mathematically. She learned the technique in a course taught by Stephen Boyd, the Stanford University professor with whom she launched the company. The 45- employee firm has raised $44 million and lined up several large clients, including chip-making giant STMicroelectronics. Bursting with ideas, Hershenson plans to apply Barcelona’s technology to a wider range of circuitry.