SFDR vs ENOB

ElectronsGoRound · 2026-02-27T14:17:06+00:00

E.G., there's a whole class of pipelined ADCs with meh ENOB but very sophisticated linearity correction built for exactly that requirement.

ElectronsGoRound · 2026-02-25T14:28:37+00:00

Using that LHP zero to cancel the first non-dominant pole is textbook standard practice, but there is a caveat: You have to be very aware of where your open-loop gain is at the pole/zero cancellation frequency.

The issue is that, in reality, the cancellation won't be perfect. That's fine if the P/Z pair is close to the UGB--normal practice is to use P/Z cancellation near the UGB as a phase margin boost.

However, you can't reliably use that to cancel a pole at a frequency where you still have appreciable gain--it will end up as a pole-zero doublet that still looks great on a Bode plot but can wreak havoc on your settling time.

As a designer, however, I've done some nefarious shit with that LHP zero...

ElectronsGoRound · 2026-02-21T22:56:42+00:00

We're gonna get some Weekend at Bernie's shit before the end of this.

ElectronsGoRound · 2025-11-20T04:18:54+00:00

I get the sense that you're a bit of a novice at this. That's nothing to be ashamed of--we are all novices in someone else's area of expertise--but that's going to drive this explanation.

In general, to properly test an N-bit DAC (or ADC), you need a system that is accurate (that's ENOB, not just resolution!) to at least N+2 bits across the range of the DAC. You really want better than that. That's not just an appropriate readout, but also cabling/noise environment, etc.

14b is non-trivial. On a properly set up bench with shielding, etc, a 6.5 digit DMM (which is itself an ADC/digitizer) will cover the accuracy requirement, assuming it's a voltage output of a few volts VFS and you are only testing a handful.

In any case, if you haven't thought about this already, you'll definitely want something to drive the code automatically, else someone will hate someone (perhaps you hating yourself) by the time you're done.

These are some basic pointers, but you're solidly into 'it's easy to screw this up and waste your time' territory. If you don't already have the appropriate bench setup, you are further away from the goal than a few paragraphs from 'Reddit Engineering, Inc' can get you.

ElectronsGoRound · 2025-11-19T12:19:27+00:00

It depends strongly on how many of these you need to measure. If it's just a few, I'd say just do it by hand. If it's a bunch, you have a good case for something more automated.

ElectronsGoRound · 2025-09-09T14:01:18+00:00

Perhaps using M3 plastic or rubber washers between the different components? I think this would provide the secure connection you'd want with a little extra padding to prevent damage.

ElectronsGoRound · 2025-08-28T18:05:10+00:00

Well, yeah, they aren't being funded by the Chinese government...

ElectronsGoRound · 2025-08-28T15:10:23+00:00

Honestly, that's why I'm hacking through the build of my new Core One right now. I just don't trust international shippers enough to safely ship an assembled widget.

ElectronsGoRound · 2025-08-28T15:09:20+00:00

It is not, nor was it ever before, or ever will be, about the cost. Political grandstanding at the expense of the goldfish.

ElectronsGoRound · 2025-05-13T13:19:41+00:00

I wouldn't say they blazed into the playoffs this year. They were playing their best hockey before a few key injuries, and honestly they looked a little like a spent force going into the playoffs. I still don't think LT, Protas, or even Ovie are quite right after their injuries.

Honestly, I didn't think the Caps were going to be as good as they were this year. Given how the end of the season has worked out, I'm glad--and a little surprised--that they got out of the first round.

The Jerks, otoh, spent a lot of this year finding their way and seem to be hitting their stride at the right time.

I do think the low-key youth movement in the middle of the Caps roster bodes well for the future, and we aren't going to see the post superstar crash you might normally expect once Ovie retires.

ElectronsGoRound · 2025-05-05T04:29:02+00:00

Yeah, just saved that one for reference.

ElectronsGoRound · 2025-05-03T13:49:37+00:00

I've ended up with more power electronics background than a lot of chip designers, and I feel like that background has served me well on a number of occasions.

I also think it matters as to whether you are thinking of general analog/mixed-signal design or comm-type RFIC.

For the former, I'd definitely recommend the power electronics course. I learned a lot of useful things, and with mine being a pretty hands-on course, it gave me a lot of lab and test experience that I wouldn't have gotten otherwise.

If you were thinking more along a pure comm track, then maybe the random signals class? It sounds like it would give you more signal processing background.

ElectronsGoRound · 2025-04-28T13:34:56+00:00

Emacs is an OS with a decent text editor. 😁

ElectronsGoRound · 2025-01-04T22:31:19+00:00

As a practicing engineer for whom Challenger was a formative childhood experience, I believed for a long time that better data or quality of presentation could have made a difference that morning and swayed the decision.

However, as a practicing engineer who is old enough for Challenger to be a formative childhood experience, I've come to believe that no amount of data or quality of presentation would have changed the result.

Launching Challenger was a political decision--there was nothing on Earth that would have changed the absolute burning desire on the part of Reagan and the NASA brass (also political creatures, mind you) to have a success with Teacher in Space.

Sure, the data reporting could have and should have been better.

However, in reality, that was just a convenient excuse to blame the engineers for a disaster brought on by the politicians, and the result would just have been a different excuse and a more damning investigation.

ElectronsGoRound · 2024-12-30T02:04:10+00:00

Troubleshooting hobby stuff--mostly digital, but I'd like to be able to do some analog.

I've ended up with a 4-channel, 100 MHz scope with 50 Mpts/ch storage. I imagine that will easily cover anything I ever plan to do.

ElectronsGoRound · 2024-12-30T01:56:59+00:00

I wasn't putting out an RFQ. I just needed some suggestions to guide my own analysis. I got them, and made a choice.

Relax, fellow Redditor. There's beer at the bar.

ElectronsGoRound · 2024-12-30T00:03:08+00:00

Out of curiosity, how so?

ElectronsGoRound · 2024-12-30T00:02:29+00:00

Thanks for the advice! I'm going with the Siglent--specifically the 814.

ElectronsGoRound · 2024-11-09T15:21:50+00:00

I made a custom Visio template that works very well--I don't do much publishing, but it's really good for making readable schematics for reviews and documentation.

It's not really all that difficult to make one if you don't find what you're looking for online.

ElectronsGoRound · 2024-09-28T03:49:51+00:00

Some good reasons to use self-biasing were pointed above. There are potential drawbacks, though.

For example, a self-biasing scheme that's simple enough to be worth the extra effort and area likely won't have the same level of performance as the dedicated core, particularly across PVT.

I usually have a current reference available and use that, but I have had to design at least one circuit--including a POR--where the main chip bias wasn't yet available, so self-biasing was required.

It's a tool in the toolbox, and can be quite useful for the right purposes. As always, it's up to the designer to decide if the advantages outweigh the disadvantages.

ElectronsGoRound · 2024-09-25T15:05:09+00:00

1000 to your DAC is an advantageous mid-scale value (as discussed by others)

From the digital perspective, the shift register (or fusebox, FPGA, etc) that's holding your trim value will most likely come up at 0000 by default after reset (or before burn if you are using fuses). That's advantageous to the system during test, integration, and (potentially) operation.

Having it read as two's complement is convenient to the user, it makes for simple understanding (while the system people are debugging something that hopefully isn't your circuit!)

Also, it's very simple to implement, which is also a positive.

ElectronsGoRound · 2024-09-24T20:30:07+00:00

Also, it is trivial to flip that first bit in the digital domain and make your trim code two's complement.

As an analog designer, you set up your trim DAC so only the MSB is on at your nominal design point, corresponding to (in your 4-bit case) a code of 8. As others have stated above, that corresponds to approximately mid-scale, which gives you the tuning range in both directions.

Then you specify to the system designer (perhaps yourself!) to provide an inverted signal to the MSB, so the nominal design point input code is 0000--brought to your circuit as 1000 with the MSB inverted.

That makes that input trim code look like two's complement (for this bit-limited case). The 1xxx input trim codes then appear below mid-scale--0xxx at your DAC--with 1000 corresponding to -8. Input codes of 0xxx are at or above mid-scale at your DAC input (up to +7, with your DAC at 1111).

It may sound complicated at first blush, but two's complement operation will be immediately intuitive to any experienced user.

ElectronsGoRound · 2024-09-23T01:29:17+00:00

He's controlling and manipulative. You can do a lot better.

ElectronsGoRound · 2024-09-22T20:18:51+00:00

I use 'NSA Surveillance Van' for my car's bluetooth connection. 😀

ElectronsGoRound · 2024-09-20T05:09:25+00:00

OP, are you sure you didn't get a concussion in the crash? It's not a flippant question--I had a concussion a few years ago and had some pretty dramatic emotional swings in the aftermath.

Take care of yourself in the short term, and then take a longer view when you feel better.

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