The December 2022 issue of IEEE Spectrum is here!

Close bar

Chip Hall of Fame: Fairchild Semiconductor μA741 Op-Amp

This chip became the de facto standard for analog amplifier ICs. Still in production, it’s available everywhere there are electronics

2 min read
Photo of Fairchild Semiconductor μA741 Op-Amp
David Fullagar

Operational amplifiers are the sliced bread of analog design. You can slap them together with almost anything and get something satisfying. Designers use them to make audio and video preamplifiers, voltage comparators, precision rectifiers, and many other subsystems essential to everyday electronics.

μA741
Op-Amp

Manufacturer: Fairchild Semiconductor

Category: Amplifiers and Audio

Year: 1968

In 1963, a 26-year-old engineer named Robert Widlar designed the first monolithic op-amp integrated circuit, the μA702, at Fairchild Semiconductor. It sold for US $300 a pop. Widlar followed up with an improved design, the μA709, cutting the cost to $70 and making the chip a huge commercial success. The story goes that the freewheeling Widlar then asked for a raise. When he didn't get it, he quit. National Semiconductor (now part of Texas Instruments) was only too happy to scoop up a guy who was then helping establish the discipline of analog IC design. In 1967, Widlar created an even better op-amp for National, the LM101, a version of which is still in production.

While Fairchild managers fretted about the sudden Widlar-powered competition, over at Fairchild's R&D lab a recent hire, David Fullagar, scrutinized the LM101. He realized that the chip, however brilliant, had a couple of drawbacks. The biggest of these was that the IC's input stage, the so-called front end, was overly sensitive to noise in some chips, because of semiconductor quality variations.

“The front end looked kind of kludgy," he says.

Fullagar embarked on his own design. The solution to the front end problem turned out to be profoundly simple—“it just came to me, I don't know, driving to Tahoe"—and consisted of a couple of extra transistors. That additional circuitry made the amplification smoother and consistent from chip to chip.

Fullagar took his design to the head of R&D at Fairchild, a guy named Gordon Moore, who sent it to the company's commercial division. The new chip, the μA741, would become the standard for op-amps. The IC—and variants created by Fairchild's competitors—have sold in the hundreds of millions. Now, for $300—the price tag of that primordial 702 op-amp—you can get about 2,000 of today's 741 chips.

The Conversation (0)

How Ted Hoff Invented the First Microprocessor

Hoff thought designing 12 custom chips for a calculator was crazy, so he created the Intel 4004

14 min read
Horizontal
How Ted Hoff Invented the First Microprocessor
DarkGray

The rays of the rising sun have barely reached the foothills of Silicon Valley, but Marcian E. (Ted) Hoff Jr. is already up to his elbows in electronic parts, digging through stacks of dusty circuit boards. This is the monthly flea market at Foothill College, and he rarely misses it.

Ted Hoff is part of electronics industry legend. While a research manager at Intel Corp., then based in Mountain View, he realized that silicon technology had advanced to the point that, with careful engineering, a complete central processor could fit on a chip. Teaming up with Stanley Mazor and Federico Faggin, he created the first commercial microprocessor, the Intel 4004.

Keep Reading ↓Show less