Electronic Design
Serendipity Stimulates Shifty Idea

Serendipity Stimulates Shifty Idea

An old bit of advice says that luck happens when opportunity meets preparedness. That seems to have been the case for Erik Matlin’s single-op-amp, single-supply level shifter (see “Non-Inverting Level Shifter Requires Only One Op Amp, One Supply Voltage”). The IFD’s inspiration, Matlin says, came when he was browsing through a collection of old application notes. One triggered a question in his mind, preparing the way for the opportunity when another would allow him to devise an answer.

At the time he formulated this IFD, Matlin was working as a customer applications engineer for Maxim Integrated Technology. (He has since returned to UCSC to pursue graduate education.) He was expanding his background knowledge by reading through some old application notes when he came across the design of a level shifter for video signals that required two op amps. Knowing that video now sees widespread use in portable devices, he wondered if the level shifter could be made smaller.

A second application note helped give him the answer. The note from National Semiconductor described a non-inverting summing amplifier using a single op amp. Matlin realized that he could use a dc reference as one of the signals into the summing amplifier so the amplifier output would simply be an offset version of the other signal.

The rest was simply a matter of working out the details. He created a reference circuit that would meet the bias current requirements on the op amp, and he needed to configure the amplifier to prevent the offset video signal from clipping. Because the original inspiration was a video application, he designed the circuit for 75-Ω output impedance.

Matlin breadboarded his design to prove it would work, then wrote it up and sent it in without much expectation of acceptance or any further development. He noted that the approach could work equally well for all kinds of applications needing a simple offset, but was still mildly surprised when it was picked for publication and even more surprised to learn that his idea was so popular.

No pressing design challenge motivated Matlin when he devised this IFD. It was just serendipity that his browsing first inspired a question and then inspired a solution. But while luck was involved, action turned the experience into one of this year’s top IFDs.

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