Hacker News new | ask | show | jobs
by vvanders 2512 days ago
The specs on the op amps aren't particularly impressive. The unity gain is 18Mhz which wouldn't be able to even keep up with a modern AVR clock(16-20Mhz). You can find discrete parts with similar specs for sub-$1.

It's a neat idea and all but when it comes to the analog design space there is a lot more variables to consider and constraints that drive them.

Your average FPGA on the other hand is able to synthesize multiple 8-bit micros and benefits from wide parallelization, I don't see similar benefits with this approach.

4 comments

Sure, but analog processing happens continuously and at an SNR that is equivalent to a very high bit depth. If you had an analog processing chain with 18MHz of BW (which granted you'd need somewhat more GBP), that would be more akin to a digital system that can produce output samples at 40Msps+. If each output sample needed even just a few dozen processing clocks to compute, you're already looking at a 500MHz+ clock. Although you could build that digital solution, it wouldn't surprise me if the analog solution was significantly lower power.
> analog processing happens continuously and at an SNR that is equivalent to a very high bit depth

16 bits is roughly 100dB, and achieving more than that is usually a serious engineering challenge. I'd like to see crosstalk rejection numbers for this system.

There are people working in the other direction, trying to use analogue for implementing the calculations of neural nets, and they tend to target the equivalent of 8 bit depth.

Yes, but I don't think your refuted my point. 16 bits (96dB SNR) is pretty good for an 18MHz signal processing system. Comparing it to a 18MHz 8bit AVR with a 10bit, 15ksps ADC is probably missing what makes this potentially cool.

Don't get me wrong, I think this is a pretty niche thing that doesn't have a lot of applications. DSP is great, and it's not going to get overthrown anytime soon. But if you were looking for things that make signal processing in the analog domain exciting to think about, I stand by high equivalent bit depth for the processing bandwidth and power consumed as a valid advantage.

> The unity gain is 18Mhz which wouldn't be able to even keep up with a modern AVR clock(16-20Mhz).

Analog constraints are much different than digital ones. If you're expecting to do anything on the 18MHz range you wouldn't be looking at this product.

But in practice I'd doubt you would be using it for anything > 100kHz, maybe 1MHz. Which is absolutely fine for most applications this is intended.

If you're really targeting anything analog > 1MHz you really should know what you're getting into, and you wouldn't be looking at a board like this.

If you know nothing about circuits, this looks cool. I guess there's always the hobby Blinkenlight crowd.
The concept of a field-programmable-ANALOG-array (FPAA) bubbles up to the surface every once in a while. I think it's a neat idea with some interesting use-cases.

Motorola had an FPAA product back in the 90's, but it never gained market traction and was aimed primarily at education.

I wonder now that FPGA's have gotten so powerful and large if it isn't possible to just simulate specific analog parts and "wire" them together into "analog circuits" to rapidly prototype analog designs? This would be different from simulation on a computer because the simulated analog FPGA circuit could actually be used, evaluated and tweaked in the field. Then, when the design is mature one could realize it using actual analog components.

I know slightly more than nothing about analog/digital signal processing, so I get your point about the ZRNA probably not being the savior of the analog signal world...

That being said, you underestimate the "Blinkenlight crowd". There are not only hobbyists, but also researchers, who do not have years of EE education and experience, but want/need to cobble together hardware and software to do their research. Preferably without going back to school for a couple of years.

I can totally see where the ZRNA might save you some time. It's often not at all that easy to vary signal processing parameters across or within experiments.

When you look at an art form like "blinkenlights" and see exclusively meaningless junks and technobabble, don't see it as a failure. See it as an opportunity.
>The unity gain is 18Mhz which wouldn't be able to even keep up with a modern AVR clock(16-20Mhz).

I am not sure what this implies; would you be able to build an equivalent, digital circuit (with presumably a ADC and a DAC stage) with an average AVR then? Or what's the clock comparison for?

The unit gain (for an OpAmp at least) is related to the bandwidth, the gain decreases linearly (in the dB scale) as the frequency goes up.

You want to be looking at the -3dB range to know +/- the actual useful bandwidth

Okay, but I'm still confused as to why would you compare it to AVR frequency; was that just a random comparison ("this car goes so slow you could outrun it") or would the frequency of a MCU clock being higher than the bandwidth of an op amp ever be important?
Correct, the comparison makes no sense

> would the frequency of a MCU clock being higher than the bandwidth of an op amp ever be important

Unless you specifically want to capture the analog waveform of the clock signal of that processor, it is unimportant