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Happy 50th Birthday to the Signetics 555 Timer IC

A Tribute to Hans Camenzind, an Extraordinary Analog Engineer

Signetics announced the NE555 timer/oscillator IC in 1972, 50 years ago. Over five decades, this simple 8-pin chip has consistently sold in the billions, each year. It’s a perennial hobbyist favorite. Well-known authors such as Walter Jung wrote 555 timer cookbooks, and 555 circuits have been popular for new circuit designs since the 1970s. Engineering acceptance has been mixed. Some engineers routinely put 555 chips in their circuits. Others view the 555 timer IC as a somewhat sloppy way to create an oscillator or a timer. However, the 555 IC’s success cannot be denied. They’re everywhere. There are even spacecraft carrying space-qualified 555 timer chips through outer space. The 555 timer is clearly one of the most successful chip designs, linear or digital, that was ever invented. 

The 555 timer was designed in 1971 by Hans Camenzind, who had hand-picked and joined Signetics in 1968, specifically because he wanted to develop linear ICs, which was one of the company’s major product lines. He picked Signetics after interviewing with every linear chip maker at the time: Fairchild, Motorola Semiconductor, Texas Instruments, Signetics, Sprague, Sylvania, and Westinghouse. I’d say that was quite a thorough search.

The idea for the 555 timer/oscillator chip grew out of Camenzind’s earlier electronics experiences. He grew up in Zurich, Switzerland and learned to fix radios before he went to college. He and his wife moved to the US in 1960, and he earned an MSEE from Northeastern University in Boston. He then joined PR Mallory and Company, which chiefly specialized in developing and selling batteries. Camenzind joined the company’s Laboratory for Physical Science, so he was involved in basic research. 

This position allowed Camenzind to explore any topic that tickled his fancy. He decided to focus on shrinking an entire radio to one chip and quickly focused on eliminating inductors from the basic radio design. He went looking for solutions:

“I went to the MIT library.  I had access to this library, and underneath the circular white dome, on the 6th and 7th floor, I spent almost a week looking through old issues of the Proceedings of the IRE (Institute of Radio Engineers). There was no index, no computer search, so I had to go through volume after volume.  I came across a concept called a phase locked loop [PLL].  I had never heard of it before. I looked at it and it was a very obscure concept, it was used to lock on to some faint signal. I think NASA used this to lock on to signals coming back from the moon for the lunar landing.”

However, PR Mallory wasn’t interested in commercializing these ideas, which drove Camenzind to Silicon Valley and Signetics. He lobbied Signetics to allow him to continue working on PLLs and soon designed the NE565 and 566 PLLs.

Camenzind had joined Signetics because he thought the company would give Fairchild Semiconductor some serious competition in the linear IC arena. But, by 1970, he felt that Signetics had lost its way, so he resigned from the company, thinking he’d write a book. He became an independent consultant and IC designer, and Signetics became his first customer. The 555 timer was his first consulting gig with Signetics, and he designed the chip’s circuit and created its physical layout. That’s how it was in the Wild West days of Silicon Valley.

Here’s how Camenzind described the situation in an oral history with the Semiconductor Museum:

“They paid $1200 a month for a year and loaned me some of the equipment, which they didn’t need, since they had just lost 50% of their engineers. So, it was an ideal situation.

“Looking back, I’m surprised that I took that risk. I had a wife and four children at home, $400 in the bank, and I had been making $18,000 at Signetics, so this would be done to $14,400.  But I quickly got two more contracts, so this worked out very well.”

Camenzind needed about a year to design the 555 timer IC. He had a working breadboard in 1971 and then laid out the chip using 10-micron design rules. He hand-cut the Rubylith masks with a razor knife. 

Signetics did not patent the device because it did not want and likely could not afford to fight the lawsuits that might arise. Companies like Fairchild had large patent portfolios and weren’t afraid to use them as a potent weapon against troublesome competitors. Silicon Valley companies routinely copied the successful designs of competitors back then; it’s how things were done. Because Signetics didn’t patent the design, copies of the 555 timer chip appeared in less than a year.

In an amusing twist, Camenzind did not think that the 555 timer IC was a very good design. As he says in his oral history with the Semiconductor Museum:

“The thing is that this is not a good design (the 555). I had a few years of experience, I’d say about five years, but I had no teacher, and I had to learn it by myself. You know it was really the beginning of [IC] design, so looking at it now, I would say ‘I wouldn’t do it like that again.’”

Despite Camenzind’s opinion of his own design, the 555 timer chip has easily outlasted Signetics by several decades. Philips Semiconductors (which was spun off and renamed NXP in 2006) acquired Signetics in 1975 and eventually retired the brand. However, you can still buy a 555 timer IC for less than a dollar in single unit quantities from a distributor like DigiKey, for example. The chip you purchase today is just as useful as it ever was; it just won’t be a Signetics 555. It will be a descendant. Versions of the 555 timer have been or are still being made by dozens of major semiconductor vendors, including Texas Instruments, Intersil, Maxim, Avago, Exar, Fairchild, NXP, and STMicroelectronics.

In a world gone digital, it’s often hard to understand the stalwarts who have stuck by analog design as Camenzind did. Today, we cannot ask him for an explanation, because he passed away in 2012. However he explained his obsession with linear circuits in the forward to his book, “Designing Analog Chips”:

“Everything is going digital. Cell phones, television, video disks, hearing aids, motor controls, audio amplifiers, toys, printers, what have you. Analog design is obsolete, or will be shortly. Or so most people think.

“Imminent death has been predicted for analog since the advent of the PC. But it is still here; in fact, analog ICs have been growing at almost exactly the same rate as digital ones. A digital video disk player has more analog content than the (analog) VCR ever did.

“The explanation is rather simple: the world is fundamentally analog.

“Hearing is analog. Vision, taste, touch, smell, analog all. So is lifting and walking. Generators, motors, loud-speakers, microphones, solenoids, batteries, antennas, lamps, LEDs, laser diodes, sensors are fundamentally analog components.

“The digital revolution is constructed on top of an analog reality.”

One thought on “Happy 50th Birthday to the Signetics 555 Timer IC”

  1. Good article. Brings back a flood of memories of when I was a “digital” chip designer at Cal-Tex Semiconductor (purchased by Fairchild) during those times.

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