Analog ASIC Design Built Using Digital Standard Cells

Tiny Tapeout is a way for students, hobbyists, and home gamers to get their own ASICs designs fabbed into real custom chips. Tiny Tapeout 3 was the third running, with designs mandated to be made up of simple digital standard cells. Only, a guy by the name of [Harald Pretl] found a way to make an analog circuit using these digital cells anyway.

In a video on YouTube, [Harald] gave an interview on how he was able to create a temperature sensor within the constraints of the Tiny Tapeout 3 requirements. The sensor has a range of -30 C to 120 C, albeit in a relatively crude resolution of 5 degrees C. The sensor works by timing the discharge of a pre-charged parasitic capacitor, with the discharge current being the subthreshold current of a MOSFET, which is highly dependent on temperature.  [Harald] goes deep into the details on how the design achieves its full functionality using the pre-defined digital cells available in the Tiny Tapeout 3 production run.

You can checkout a deeper breakdown of [Harald]’s design on the submission page. Meanwhile, Tiny Tapeout creator [Matt Venn] gave a great talk on the technology at Hackaday Supercon last year.

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QSPICE Picks Up Where LTSpice Left Us

[Mike Engelhardt] is a name that should be very familiar to the hardcore electronics nerd. [Mike] is the developer responsible for LTSpice, which is quite likely the most widely used spice-compatible simulator in the free software domain. When you move away from digital electronics and the comfort of software with its helpful IDEs and toolchains, and dip a wary toe into the murky grey waters of analog or power electronics, LTSpice is your best friend. And, like all best friends, it’s a bit quirky, but it always has your back. Sadly, LTSpice development seems to have stalled some years ago, but luckily for us [Mike] has been busy on the successor, QSpice, under the watchful eye of Qorvo.

It does look in its early stages, but from a useability point of view, it’s much improved over LTSpice. Performance is excellent (based on this scribe’s limited testing while mobile.) Gone (thankfully!) is the uncommon verb-noun usage paradigm — replaced with a more usual cut-n-paste flow. Visually it still kind of looks like LTspice in places, but nicer with a clear and uncluttered design that gets straight to the point. Internally, the simulation engine has improved in speed and accuracy, as well as adding native support for modern semiconductor types, such as wide bandgap materials like SiC. Noted is that this updated software has a particular emphasis on power integrity and noise analysis, which are sticky problems that have a big impact on modern high-power systems.

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The Right Equipment Makes A Difference For Digital Oscilloscope Music

We all love our cheap digital oscilloscopes, and with good reason. But if there’s one place where analog scopes still shine, it’s anywhere you need X-Y mode. Digitally sampling the inputs and mapping them on the screen as discrete points just isn’t the same as steering an electron beam around a CRT, making X-Y mode work on digital scopes — at least the affordable ones — somewhat lacking.

Thankfully, nobody told [Mark Hughes] that his digital scope would make a lousy X-Y display, so he just plunged ahead and figured out how to make it work anyway. The results are actually pretty good, but it took some doing. His setup begins with OsciStudio, an application built to take 3D shapes and animations and turn them into oscilloscope music. The output from that is piped to a USB sound card; [Mark] used a PreSonus Studio 26c, an adapter with DC-coupled inputs, which he found to be critical to getting good images. Also important was a USB isolator and good-quality cables, which greatly reduced jitter and made the image much more stable.

Displaying the image was as easy as connecting the left and right outputs from the sound card to the two scope inputs — [Mark] used a Keysight EDUX1052G — and setting it to X-Y mode. It took a fair amount of fiddling to get as far as he did, but we think the results speak for themselves. As for the sounds made by these images, he says it’s a bit like a hung sound card when a computer blue-screens. So, yeah — not exactly musical, but still an interesting way to have some fun with your digital scope.

Freq Out With LTSpice

We always enjoy [FesZ’s] videos, and his latest about FREQ function in LTSpice is no exception. In fact, LTSpice doesn’t document it, but it is part of the underlying Spice system. So, of course, you can figure it out or just watch the video below. The FREQ keyword allows you to change component attributes in a frequency-depended way.

Of course, capacitors and inductors are frequency dependent by design. But the FREQ technique allows you to adjust things like voltage sources or resistance in arbitrary ways. By default, you must specify the frequency response data in decibels, which isn’t always convenient. However, [FesZ] shows you how to use other methods to express them using modifiers to the command.

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Congratulations To Our Op-Amp Challenge Winners!

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…

The Winners

[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!

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A Modular Analogue Computer

We are all used to modular construction in the analogue synth world, to the extent that there’s an accepted standard for it in EuroRack. But the same techniques are just as useful wherever else analogue circuits need to be configured on the fly, such as in an analogue computer. It’s something [Rainer Glaschick] has pursued, with his Flexible Analog Computer, an analogue computer made from a set of modules mounted on breadboard strips.

Standard modules are an adder and an integrator, with the adder also having inverter, comparator, and precision rectifier functions. The various functions can be easily configured by means of jumpers, and there are digital switches on board to enable or disable outputs and inputs. he’s set up a moon landing example to demonstrate the machine in practice.

We’re not going to pretend to be analogue computer experts here at Hackaday,but we naturally welcome any foray into analogue circuitry lest it become a lost art. If you’d like to experiment with analogue computing there are other projects out there to whet your appetite, and of course they don’t even need to be electronic.

Recreating An Analog TV Test Pattern

While most countries have switched to digital broadcasting, and most broadcasts themselves have programming on 24/7 now, it’s hard to remember the ancient times of analog broadcasts that would eventually stop sometime late at night, displaying a test pattern instead of infomercials or reruns of an old sitcom. They were useful for various technical reasons including calibrating the analog signals. Some test patterns were simply camera feeds of physical cards, but if you wanted the most accurate and reliable test patterns you’d need a Philips pattern generator which created the pattern with hardware instead, and you can build your own now because the designs for these devices were recently open-sourced. Continue reading “Recreating An Analog TV Test Pattern”