Fairchilds Ua702 Bob Widlars First Monolithic Operational Amplifier

# Fairchild's uA702: Bob Widlar's First Monolithic Operational Amplifier

## 1. A First Attempt at Putting an Amplifier on One Die

Bob Widlar, working at Fairchild Semiconductor in the early-to-mid 1960s, designed the uA702, generally credited as the first commercially produced monolithic operational amplifier: a general-purpose analog building block, built entirely on one silicon die, that could amplify a small input signal difference with the high gain and reasonably stable behavior earlier discrete-transistor amplifier designs required a circuit board full of matched components to approach.

The uA702 proved the basic case that a usable operational amplifier could be built as a single integrated circuit at all, but it carried real limitations: a narrow input voltage range, modest output drive capability, and a degree of temperature sensitivity that kept it from becoming the broadly adopted catalog part a later design would become.

## 2. Widlar's Specific Contribution

Widlar work on the uA702 is notable in the history of analog integrated-circuit design specifically because it combined circuit techniques developed for discrete designs with an understanding of what the monolithic fabrication process could and could not hold consistent across a die — a combination that let an amplifier design survive being shrunk onto one piece of silicon without losing the performance discrete designers depended on.