WStephenWoodward

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Design Development Engineer

With more than 50 contributions to his credit, Steve Woodward is one of EDN's most prolific Design Ideas authors. His offerings started in 1974 with an idea entitled "Simple 10-kHz V/F features differential inputs," for which he won the annual prize for the best Design Idea. As a self-proclaimed "certified, card-carrying analog dinosaur," most of Woodward's ideas solve issues in that nebulous "nondigital" area of design engineering that gives us the thorniest problems. His Design Idea titles, such as "Self-heated transistor digitizes airflow" in 1996 and "Circuit controls microneedle etching" in 2003 demonstrate how he likes to adopt electronics to the physical world. Woodward is an instrumentation, sensors, and metrology freelance consultant to organizations such as Agilent Technologies, The Jet Propulsion Laboratory, the Woods Hole Oceanographic Institute, Catalyst Semiconductor, Oak Crest Science Institute, and several international universities. With seven patents to his credit, he has authored more than 200 professional articles. He has also served as a member of technical staff at the University of North Carolina. He lives with his wife, Clare, and sons in NC.


WStephenWoodward

's contributions
  • 12.20.2017
  • Inverted dual-slope ADC boosts dynamic range
  • Thanks for the comments, John. But I think a bit of research will reveal that the term "Dual Slope Integrating ADC" has never been used in the way you suggest. Early efforts to use analog integrators for data translation included "Single Slope Integration." in which a reference was integrated while an analog comparator compared the ramp generated to Vin. Thus a counting interval was generated that was directly proportional to Vin, not inversely as in my design. Meanwhile, as for the practical utility of this concept, I suggest a quick read of this US utility patent: http://pdfpiw.uspto.gov/.piw?docid=05723783&PageNum=4&IDKey=3CD00396C765&HomeUrl=http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1%2526Sect2=HITOFF%2526d=PALL%2526p=1%2526u=%25252Fnetahtml%25252FPTO%25252Fsrchnum.htm%2526r=1%2526f=G%2526l=50%2526s1=5723783.PN.%2526OS=PN/5723783%2526RS=PN/5723783 The flowmeter invention it describes is based on the RDSADC concept, and was embodied in successful products sold over the ~20yr life of the patent, resulting in the profitable manufacture and sale of ~30,000 units. So, sorry John, but I think the concept has in fact been rather well proven in practice. Cheers, Steve
  • 11.28.2017
  • Cancel PWM DAC ripple with analog subtraction
  • I agree with both Brian and Dave that there's more than one way to defrock this particular feline. Thanks for your contributions. However, please note that both your suggestions are not only compatible with each other, but can also be combined with my analog subtraction DI to get the ripple-reducing benefits of any two or all three.
  • 11.28.2017
  • Cancel PWM DAC ripple with analog subtraction
  • Good question, Stu! Looks like the EDN web elves decided you could just rely on my oh-so "picturesque" text and your imagination. Meanwhile, see if this works: http://i68.tinypic.com/2gt9s82.jpg
  • 07.29.2016
  • Circuit delivers constant power to a load
  • Late to the party, but why not just connect your capacitor C between your heater R and a variable-frequency F squarewave generator V? Then, so long as F is much slower than 1/RC, the pure AC power delivered to R will be... P = V^2 F C ...with less complexity and 100% efficiency.