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Miniature portable electronics—cell phones, music players, pocket media centers—all rely on battery-saving power-management devices. These low-dropout voltage regulators (LDOs) invariably use a series-pass transistor—a power MOSFET—whose efficiency is critical to the portable's battery life. Look closely enough here, and you'll find the footprint of Richard Williams, an engineer who continues to streamline the operation of MOSFETs and voltage regulators.
MOSFET makers have long known that you can lower on-resistance, increase current capacity and reduce heat dissipation by paralleling MOSFET cells. But they didn't know how to do it without increasing the vulnerability of those cells. Williams taught them. At Vishay Siliconix, he had created a bleeder diode (think "steam valve") to prevent punch-throughs. That paved the way for continued breakthroughs in MOSFET and voltage regulator efficiency and miniature packaging—advances that Williams continues to apply to new-generation sub-1-volt LDOs at Advanced Analogic Technologies Inc.
There, Williams figured out how to manufacture MOSFETs on a memory process. That coup not only gave sub-1-V LDOs the precise geometry they needed for efficiency and minimal heat dissipation, but it also allowed the high-volume, low-cost manufacturing that's consistent with the demands of modern portables.
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