Some of the most important chips in the first mobile phone boom came from Greensboro, North Carolina, far from Silicon Valley. RF Micro Devices made the radio frequency parts that amplify a phone's signal and send it to the nearest tower. It built them from gallium arsenide, a material that handles high frequencies better than ordinary silicon. When RF Micro went public in June 1997, cell phones were turning from car-mounted luxuries into things people carried in a pocket.

Gallium Arsenide in Greensboro

William Pratt, Powell Seymour and Jerry Neal founded RF Micro Devices in 1991. They licensed a gallium arsenide transistor process and designed power amplifiers and other radio chips around it. The parts were small and efficient, which meant longer battery life and smaller phones. Phone makers needed several such chips in every handset. RF Micro's bet was that wireless would grow fast enough to make a specialist chipmaker in North Carolina a large company.

Becoming Qorvo

RF Micro priced its IPO at $12 a share in June 1997 on Nasdaq. Its sales rose with the spread of mobile phones, and its customers grew to include most of the large handset makers. The work got harder as phones packed in more radio bands and buyers pushed prices down. In 2015 RF Micro merged with TriQuint Semiconductor, a rival radio chipmaker, to form Qorvo.

Cover: Valley of Aosta: Snowstorm, Avalanche, and Thunderstorm, Joseph Mallord William Turner. Art Institute of Chicago, public domain. Chosen for a thunderstorm over the Alps (energy sent through the air).