Category Archives: Reader questions

Reader question: Shouldn’t the (effective) bandwidth of the ADC or DAC also be reported in the titles?

Ameya Bhide posted a question in the Q&A section. Ameya wrote:

Hi Bengt,

After being lost in the world of Converters for a while, I always have this fundamental question as follows:-

Industries, Publications always talk about GSamples/sec of an ADC or a DAC and the higher the rate, better the converter is. But very few talk about the Bandwidth in the title of the ADC. Even in publications, I always see the title as ” An XGsamples/sec ADC” where as I think it should be “An X Gsamples/sec Y Mhz BW ADC” since many of these converters do not retain performance up to Nyquist.

Even when looking at the TI ADC’s I need to search the data sheet to find the real bandwidth of the ADC. Shouldn’t the sample rate and BW be always reported together so that one quickly understands what the capabilities of the ADC are?

Could you comment on this?


Good question Ameya, and one that touches on a broader topic (scientific reporting practices) that I’ve been planning to bring up for a while. This is a good starting point. Perhaps your question was mostly concerning data sheets? Either way, I’d like to broaden it to include scientific papers as well.

So blog readers, what do you think?

  • Is there an inflation in paper/data-sheet titles?
  • Should we require paper titles to more accurately describe the actual bandwidth of the ADC?
  • Is effective resolution bandwidth (ERBW) the best measure?

If there is an inflation, and a practice to boost performance in the titles, what will happen to the pioneers which put more complete (potentially less impressive) information in the titles? Rejected papers and loss of business? Is the target audience really that gullible? Don’t they read the content of a data sheet or paper? How long can a paper/data-sheet title be 😉 … etc.

Reader question(s): Novelty of folding amplifier ADC architecture, big houses approach to external innovations, and academic vs. commercial specs

Blog reader Cole posted a question in the Q&A section, and I felt it was well worth a separate post:

Hi Dr. Jonsson, I am wondering the following things in general about the ADC industry:

–Are folding amplifiers a new concept? Why when I look at the TI website, for example, they do not sell any ADCs with a folding amplifier architecture?
–How open are the big houses to outside designs? If a small design house comes up with someone innovative, do the big houses adopt, buy-out, or ignore the small houses?
–What is the main difference between academic specs and industrial specs? How would I “convert” between the two? It seems like when I read academic papers, they claim high speeds at a certain bitrate, but industrial numbers all seem a bit more conservative (i.e. MSPS rather than GSPS).

As you can see, there are several interesting questions in there. What do you think? How hot are folding ADCs today? Do you have any experience from start-up innovation in relation to the big companies? How do you translate between data sheet specs and academic paper performance?

Anyone from “the big houses” wish to comment? How would you handle great innovations emerging in a small start-up external to your company? Adopt, buy-out or ignore? And how should we view commercial data sheet specs compared to scientific papers? Should we even try to “translate” between the two, or are these better seen as parallel universes?

Reader question: What is an ADC?

You'd think that "What is an ADC?" must be a simple question to answer, right? But when scientists meet here at Converter Passion, dissection is inevitable.

Blog reader Michiel van Elzakker posted a more philosophical question in the Q&A section, and I think it deserves a dedicated post:

— “What is an ADC?

The question – at first glance seeming like a trivial entry-level question (which is also welcome here in case you wonder) – turned out to have a lot of scientific depth and potential. Michiel continues:

“There can probably be some consensus on a short answer: “Something to convert an analog input into a digital output”.

How about a long answer? Who would like to share his opinion? ;)

– Is a standard digital flip-flop in fact a very low power 1-bit ADC?
– Is it okay to use external calibration to improve an ADC’s accuracy? And if a PC performs the actual correction, does that make the PC part of the ADC?

References & supplies
– Is 0 dB power supply rejection sufficient? 10 dB? 50 dB?
– How many reference voltages can I use? I would like 2^N of them!
– Is it okay to use a reference clock? At a higher frequency than the actual sample rate?”

As I understand Michiel’s question, it is about the limits of what we would even consider calling “an ADC“, and also what constitutes a “complete ADC“. Interesting indeed! What are those limits according to you? Is the calibration PC part of the ADC? Is a flip-flop a 1-b ADC? Share your wisdom and opinions with the rest of us!

Reader question: Why is the data converter market dominated by six US companies?

Who’s making a splash in the data converter market?

The Q&A section on this blog might not be too visible, but as you can see here, it actually works: steve asks this interesting question:

Why the $3B data converter market is dominated by the six US companies: ADI, TI, Maxim, LinearTech, National Semi and Intersil. Have any one heard of any data converter companies out of the US?

… and I felt it deserved a dedicated post where you can all have your say. So, what do you all think? And what other companies have you heard of? Do you even agree with steve that it is these six that dominate? If not, who are?

Edit: I’ll be working on the list(s) below, trying to get it as complete as I possibly can. With your help it should work. Just keep suggesting data converter companies to add here. My proposal is to limit the list to companies that provide stand-alone data converters and/or data converter IP. Companies providing data-converter related design services and expert consulting could of course be interesting too, and perhaps go into a second list. [That way I can include my own company, ADMS Design too 😉 ]

Edit 2011-04-09: As you might have heard, Texas Instruments is to acquire National Semiconductor. Read more about it here.

And then there were only five … 😉

The “Big Six”

As the question was asked by steve, we get the following list of six US data converter companies – dubbed the “Big Six” by jjwikner below – that (supposedly) dominate the ADC and DAC market. Here in alphabetical order:

The list is not written in stone. Have your say below. Should it be the big 3, 4, 5, 7 instead? How about data converter IP dominance – is that a completely different list of companies? And don’t forget the original question: why are all of these companies US-based? Something in the US water? Engineering tradition? Business culture? Choice of target applications? Are the leading Asian companies keeping their designs for in-house use, or did they simply bypass the stand-alone converter phase altogether? Are they now positioning themselves for the inevitable embedded data converter era by developing IP blocks for SoC designs?

The complete list?

To the best of my knowledge, and with the kind help of my blog readers, this is the “complete list” (*) of companies offering data converter IP or stand-alone parts. Again, in alphabetical order, and with the Big Six included:

(*) Allow the list a reasonable settling time constant, and please send me an email or post a comment below if you know of any company not included in the list, or have any other remarks.

NB: I have not necessarily made an assessment of the individual companies included in the list, and the list is therefore no statement of the quality or suitability of the products/IP offered for a particular purpose, nor an endorsement of the company itself.

The list seems very US and Euro-centric, but that’s my current horizon. I’m sure there must be some Asian companies out there. Scientific activity actually suggests that Asia is going to take over this business eventually. So, please enlighten me! Where are those Asian companies?