Tutorial on the Theory, Design and Characterization of Nyquist Digital to Analog Converters

R2R_DAC

In this episode, Shahriar presents the theory, design and characterization of Nyquist Digital to Analog Converters (DACs). After a brief overview of DAC operation and theory, the schematic of an 8-Bit R-2R DAC is presented. The R-2R DAC, which is driven by a dsPIC30F6014A Microchip microcontroller  is capable of producing ramps and arbitrary waveforms uploaded through an RS232 interface. The static integral non-linearity (INL) and differential non-linearity (DNL) is measured by using a Rigol DM3068 Multimeter through a Matlab interface program. The dynamic performance of the DAC is characterized using an Analog Devices AD6645 105MSps 14-Bit ADC evaluation board coupled with a USB FIFO interface board. By using the ‘Visual Analog’ software, the spectrum of the DAC output as well as the signal to quantization and distortion ratio (SQNDR) is calculated. Finally, the impact of component mismatches, operational amplifier non-linearity and timing uncertainty on the INL/DNL and SQNDR (ENOB) of the DAC is examined.

18 comments

  1. Von says:

    I love what you guys are up too. This sort of clever work and exposure!
    Keep up the awesome works guys I’ve incorporated you guys to blogroll.

    Stop by my weblog lady in red dress

  2. Steve P says:

    A very nice blend of theory and practice. Ideas for more videos:
    – frequency counters, their trigger points, how they can deceive, importance to sanity-check on the oscilloscope, modes of use (period, A to B, etc)
    – more cryogenics: it would be interesting to see how the noise of a simple bipolar or MOS amplifier changes with temp – it should go down. Consider using dry ice for another temperature point.
    – types of noise, their spectra, what generates those kinds (white, pink, red etc). What to do about noise.
    – and how about digital signal processing?

  3. Richard says:

    Hi Shahriar – when the software displays the FFT, why doesn’t the fundamental spur start at 0db? It appears to be about -5 or 6 db, below th 0 mark. Can you explain that? Perhaps you wouldn’t mind doing one of your excellent videos on how to interpret FFT displays (choosing the correct windowing function, etc.). Thanks!

  4. A detailed level question about a phenomena that shown on the specturm analyzer waveform on the computer screen in the video…. I notice that at different intervals (many seconds) through out the video the noise floor jumps up and settles back down. This is often accompanied by the width at the base of the primary signal peak spreading wider and then narrowing back up as the nosie floor drops back down, during the times that you are not changing things. What causes this? I have seen this before in a few other places and am curious to understand it?

  5. Jim says:

    Dude, these are the best electronics engineering demos on the planet. And, you have the BEST lab setup. I love this site.

    Jim

  6. ThePhen says:

    I’m not sure if I’m going to ask this question properly. but…. When you are using all of those power supplies, circuits-under-test and the many instruments together do you have to worry about all the ground potentials in the experiment?

  7. Ed says:

    I really enjoyed the technical nature if this video.
    I vote for more videos of a higher technical nature.
    But I do enjoy them all.

    Thanks for producing these excellent educational videos.

  8. Bob says:

    Incredibly well made and informative. Thank you.

  9. Daniel says:

    First off, FANTASTIC VIDEOS, presentations and info! Keep up the great work! It is refreshing to hear someone doing electronics video blogging and also using mature, engineering language when presenting. I really appreciate your hard work on this stuff.

    Now, regarding the spam: I noticed this too. McAffee web advisor at work catches it and gives me a warning before visiting the site. They tell me that it is flagged as spam links and I have to click a button to proceed, saying ignore the risk and take me to the site anyways.

  10. Hi Shahriar,

    First of all: Awesome video! And awsome experiments!
    (And please keep it that technical..)

    Why don’t you publish your source code (uC Firmware, Matlab code, etc.) alongside the video. Or am I just blind and didn’t see it?

    On a sidenote I also wanted to share a GNU Octave Script (might need a few minor changes to work with Matlab) I wrote some years ago to simulate R-2R networks with arbitrary resistor values:

    http://svn.clifford.at/tools/trunk/electrotools/r2rcalc.octave

    The intendet use of this script was of course to analyze the effect of off resistor values on an R-2R network. So I found your video particularly interesting as I never confirmed my findings with an experiment and never looked at the results in the frequency domain.

  11. Rupert Swarbrick says:

    On a happier note: Thanks for doing this video! It was really cool to see how the various INL/DNL/SN*R parameters can be physically measured and what they really mean. Although the last measurement was really impressive, I rather enjoyed the Matlab+Multimeter example. I have a (spare) reasonably ancient 1980s bench multimeter and I think I might try to add a piggyback USB link so that I can do something similar, albeit on a rather lower budget.

    Are you planning a similar video for ADCs? That would be fascinating!

  12. Rupert Swarbrick says:

    Did you know that your page (accessed at http://thesignalpath.com/blogs/2012/12/10/tutorial-on-the-theory-design-and-characterization-of-nyquist-digital-to-analog-converters/) currently has payday loans spam at the top?

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