The real world is analog, and the op-amp is the indispensable building block of many analog circuits. We wanted to give you analog fanatics out there a chance to shine and to encourage our digital brothers and sisters to dip their toes in the murky waters where ones and zeroes define the ends of a spectrum rather than representing the only choice. Hence, we presented the Op Amp Challenge. And you did not disappoint!
We received 83 entries, and it was extraordinarily hard to pick the winners. But since we had three $150 DigiKey shopping sprees to give away, our six judges buckled down and picked their favorites. Whether or not you’ve got the Golden Rules of the ideal op-amp tattooed on your arm, you’ll enjoy looking through all of the projects here. But without further ado…
[Craig]’s Op Art is an X-Y voltage generator to plug into an oscilloscope and make classic Lissajous and other spirograph-like images, and it’s all done in analog. Maybe it was his incredible documentation, the nice use of a classic three-op-amp tunable oscillator, or the pun hidden in the title. Whatever the case, it wowed our judges and picked up a deserved place in the top three.
Hearkening back to the pre-digital dinosaur days, [Rainer Glaschick]’s Flexible Analog Computer is a modular analog computer prototyping system on a breadboard backplane. Since you have to re-wire up an analog computer for your particular, it’s great that [Rainer] gave us a bunch of examples on his website as well, including a lunar lander and classic Lorenz attractor demos.
And there was no way that [Chris]’s interactive analog LED wave array wouldn’t place in the top three. It’s a huge 2D analog simulation that runs entirely on op-amps, sensing when your hand moves across any part of its surface and radiating waves out from there. You have to admire the massive scale here, and you simply must check out the video of it in action. Glorious!
We wanted to give you plenty of room to strut your stuff, whether that was making something classic, something entirely off the wall, or something that would fit on the measurement bench at the metrology department. So here’s a quick rundown of just some of the projects that we thought were worth a look.
[Mark Omo]’s LOCKDOWN is a superb lock-in amplifier design and a great demo and explanation of how one works. Essentially, if the signal you want to measure has a periodic component – sits on a carrier wave – then you can use a lock-in amplifier to “tune in” on just the signal, and the non-periodic noise drops right out. This is an amazing build and a shoo-in for the hyper-precise mention. Plus, what a snazzy circuit board!
[Floydfish]’s ultra-low noise amplifier “Take a ‘NAP’ and enjoy a moment of silence” is a classic design, but as is always the case with precision builds, a lot depends on the details of how you do it. Here, a copper-clad cage with Mu-metal shielding is put inside a nicely labeled cookie tin to get the job done. The design pushes the chosen precision op-amp to its limits.
Until reading up on [Bruce Land]’s Model nonlinear biochem reactions using opamps, we had no idea what a repressilator was. And honestly, we’re still not sure. But [Bruce] made a purpose-built analog computer to simulate this ring of genes that suppress each other’s expression. Whoah.
And [Jarrett Cigainero]’s ADS-B on a real RADAR CRT only uses a little bit of op-amp to go from the DACs to the screen, but we just love the sweet phosphor glow, so we’re going with it.
One of the absolute classic op-amp applications is simple signal level scaling, and [David]’s ultra-low-cost pH amplifier circuit for 3.3V MCUs is a great example. [Florian Dirnberger]’s nice Triangle-wave oscillator gets the job done and is very well documented. [555TechLab] implemented a classic 0 V – 10 V variable voltage reference with one of the only 741 builds in the whole contest. And if all this op-amp stuff makes you want to know how they work under the hood, check out [Mitsuru Yamada]’s CMOS Homemade Operational Amplifier for a non-traditional take.
We haven’t run an analog design contest in years, and we’re guessing that there was a lot of pent-up demand, and we were really floored by the number and quality of entries here. Be sure to check out the big list of contest entries because we’re certain you’ll find something else that strikes your particular funny bone. Don’t get me started on the audio effects, for instance!
Congratulations to everyone who entered, especially those who took home a prize. And as always, thanks to DigiKey for sponsoring.