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Analog Squarer {Y=X^2} 1 Quardrant

Discussion in 'Electronic Design' started by Harry D, Nov 17, 2012.

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  1. Harry D

    Harry D Guest

    I have looked at the AD835 and other 4-Q multipliers but they are costly and power hogs. I need a simpler (+/-5% accuracy [-40C to 105C]) design thatwill be used in a high reliability product. Input range of 0.05V to 1.70V with a bandwidth of dc to at least 1.0MHz. Simplicity, small size, low power <50mW, SM implication and cost are a plus. I need some starter ideas for me to complete the design.

    Cheers,
    Harry
     
  2. x^2 = exp(2*ln(x))

    log-antilog with thermistor temperature compensation?


    Best regards,
    Spehro Pefhany
     
  3. Find a microcontroller with a 10Msa ADC and do the multiply in that. Will cost you max 1 USD. Then you can do more complex arithmetics


    Regards

    Klaus
     
  4. Harry D

    Harry D Guest

     
  5. Harry D

    Harry D Guest

    The MC1594 must be one of JT's old designs using Vac tubes. Normal PS is +/-15V with +/-4.0V of CM dead range so worthless in +/-5V unit.
    i shoulder added +/-5V operation is a requirement.

    Regards,
    Harry
     
  6. Harry D

    Harry D Guest

    I agree John, a nonlinear circuit would be simpler in my design. If I could design a circuit who's output would be 1/Vin with all my other requirements, that would be perfect. Trimming is not allowed, got to work in production, no tweaking, every time.
    Regards,
    Harry
     
  7. whit3rd

    whit3rd Guest

    How about LM13700 (figure 6 on the datasheet is a multiplier)?
    It's not happy at your temperature extremes, but it IS cheap
    and runs on fleapower.
     
  8. Harry D

    Harry D Guest



    Yea but that +/- 15v IC will not operate in a +/-5V domain.

    Thanks,
    Harry
     
  9. legg

    legg Guest

    Was going to say RC4200, but Fairchild dropped the ball after taking
    it from Raytheon.

    So:

    http://electronicdesign.com/article/power/what-s-all-this-multiplier-divider-stuff-anyhow-

    RL
     
  10. Fred Bartoli

    Fred Bartoli Guest

    Harry D a écrit :
    Does BW need to be 1MHz on both inputs?

    If not you could use a digipot with a small uc with an integrated ADC
    (or build your own with internal comparator) for the slow input.
     
  11. Fred Bartoli

    Fred Bartoli Guest

    Fred Bartoli a écrit :
    Sorry I missed the squarer part, only retaining the multiplier.

    Forget that.
     
  12. P E Schoen

    P E Schoen Guest

    "Harry D" wrote in message
    < hogs. I need a simpler (+/-5% accuracy [-40C to 105C]) design that will be
    used in a
    You might consider a multiplying DAC. But they are also expensive and you
    would need an A/D as well as (in some cases) an SPI interface for the
    digital input. Here is one:
    http://www.analog.com/static/imported-files/data_sheets/AD5543_5553.pdf

    The AD633 multiplier is reasonable cost but minimum +/- 8V:
    http://www.analog.com/static/imported-files/data_sheets/AD633.pdf

    I have about 15-20 pieces of AD534 in 14 pin gold/ceramic DIP I can offer
    for well under the present list prices, but it is also minimum +/- 8V.

    The best option may be a PIC with dual simultaneous high speed A/D and
    hardware multiplier. The output could be PWM or digital into an external
    DAC.

    You might be able to use the diode square law function as described here:
    http://www.philbrickarchive.org/us3373293.pdf

    or more recently:
    http://www.edn.com/file/22730-91699di.pdf

    Another technique is using PWM where the amplitude as well as the pulse
    width are derived from the signal you want to multiply.
    http://www.journal.kmutnb.ac.th/journal/182910255015101.pdf

    Also look at the LT2940, which uses a multiplier for power measurement:
    http://www.newark.com/linear-technology/lt2940cms-pbf/ic-power-current-monitor-msop-12/dp/52R9872
    http://cds.linear.com/docs/Datasheet/2940f.pdf
    http://cds.linear.com/docs/LT Journal/LTJournal-V20N2-01-df-LT2940-Mitchell_Lee.pdf

    This old post may help:
    http://sci.tech-archive.net/Archive/sci.electronics.basics/2006-08/msg00155.html

    Paul
     
  13. Robert Baer

    Robert Baer Guest

    A single diode,properly biased is fairly decent square law for a
    small range.
    Use a matrix with resistors; in the old analog daze (40+ years ago)
    they were called DFGs.
     
  14. Bill Sloman

    Bill Sloman Guest

    Interesting. He wants 1MHz and 5% accuracy, so the three inverters
    have to run faster than 20MHz with a 1.7V input Might still be a power
    hog.
     
  15. whit3rd

    whit3rd Guest

    It's tested at +/- 15V, but it works fine down to 2V or so.
    Other OTA designs (RCA/Intersil's old CA3080) were recommended
    down to +/- 2V.
     
  16. Use APSK (Amplitude and Phase Shifted Keying).
     
  17. Jasen Betts

    Jasen Betts Guest

    but that temperature range (400K +/- 20%) may not play well with
    the required +/- 5% accuracy

    the 145 degree range is worth about 290mV of bias
     
  18. legg

    legg Guest

    http://electronicdesign.com/article/power/what-s-all-this-multiplier-divider-stuff-anyhow-

    RL
     
  19. Harry D

    Harry D Guest

    Jim, As my question states, I only need one quadrant, the first or third, both inputs tied together.
    I am trying to keep a MOSFET on for as long as possible, from releasing smoke on overload conditions, so tracking the I^2*T constant of FET and also need a temperature term which is strait forward. The FET current changes 10:1 so the "time on" changes 1:100.

    Regards,
    Harry
     
  20. Tim Williams

    Tim Williams Guest

    Would it suffice to do it bolometrically?

    Feed the current into a PTC (perhaps a silicon PTC so it has the same
    tempco!) and monitor its resistance in real time. Turn off when it's too
    high.

    You can of course use the MOSFETs themselves for this, but you need to be
    able to sense the drain voltage.

    Tim

    --
    Deep Friar: a very philosophical monk.
    Website: http://seventransistorlabs.com

    Jim, As my question states, I only need one quadrant, the first or third,
    both inputs tied together.
    I am trying to keep a MOSFET on for as long as possible, from releasing
    smoke on overload conditions, so tracking the I^2*T constant of FET and
    also need a temperature term which is strait forward. The FET current
    changes 10:1 so the "time on" changes 1:100.

    Regards,
    Harry
     
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