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mV/ac to V/dc converter IC

Discussion in 'Electronic Design' started by J.Koning, Jan 20, 2006.

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  1. J.Koning

    J.Koning Guest

    I'm looking for an IC giving an output in the
    range of 0-1Vdc or 0-10Vdc at an input voltage
    of 0-10mV/ac with a frequency around 1MHz/sine.
    Supply voltages available are +/-5V and +/-15V.
    Accuracy/linearity is not that important.
    I rather prefer something simple such as a
    device with low external component count like
    integrated rectifier diodes etc.

    Can anybody help?

  2. Joerg

    Joerg Guest

    Hello Jan,
    Did you look at Analog Devices?,2879,770%5F849%5F0%5F%5F0%5F,00.html

    Regards, Joerg
  3. Fred Bloggs

    Fred Bloggs Guest

    Any single supply RRIO type like the AD8605:
    View in a fixed-width
    font such as Courier.
  4. I'm reading it as you wanting a 'precision rectifier'. With a gain of say
    Maybe a AD636 true RMS converter, preceded by 100x ac gain opamp. Use a dc
    x10 opamp to get up to a final +10Vdc.
  5. J.Koning

    J.Koning Guest

    Hi John,

    There's no need for true RMS eversince my input is a true sine.
    As mentioned, accuracy is NOT important, but high gain is.
    So, anything simple/cheap that makes 1-10Vdc out of 10mV/1Mhz.

  6. J.Koning

    J.Koning Guest,2879,770%5F849%5F0%5F%5F0%5F,00.html

    Hello Joerg,

    The AD630 could do the job, but eversince I do not need the
    accuracy it is a bit "mit Kanonen auf Spatzen schießen".
    An opamp with two suitable diodes acting as absolute
    value converter followed by an integrator comes to mind.
    But that again is a handfull of components I don't want.
    Something cheap/small with 10mV/1Mhz in and 1-10Vdc out
    and not necessarily a linear Vo=f(Vi) would be ideal.

  7. J.Koning

    J.Koning Guest

    mV/ac to V/dc converter IC ???
    All I see is a V-follower.
    Did you read the question Fred?
    Or do I miss something?

  8. Fred Bloggs

    Fred Bloggs Guest

    You can put a little gain in there and drive it into an RC filter for
    the smoothing. The trick is to apply the majority of gain into
    amplifying a DC signal and not an ac-signal. You can do that these days
    with these ultra-low Vos amps.
  9. Fred Bloggs

    Fred Bloggs Guest

    And that amp is wired between V+ and GND so its output clamps at 0.000V
    under light loading on the negative input excursions.
  10. Fred Bartoli

    Fred Bartoli Guest

    I guess you missed something. OTOH he didn't clearly tell you to supply the
    opamp between GND and +5V. But if had looked at the datasheet you'll have
    seen it's a 5V/single supply opamp.

    But this probably won't work as such for your 1MHz signal (look at fig 27. /
    1.5us recovery time).
    Supplying it between -5V and GND, or having your referenced your AC signal
    to the +5V supply rail will buy you a much better recovery time (see fig 26)
    and might work OK.
  11. J.Koning

    J.Koning Guest

    OK, obviously I missed that one but now I'm with you.
    Good idea, certainly for that price, I'll give it a try.

  12. Joerg

    Joerg Guest

    Hello Jan,

    True, it's a lot of money just for that function.

    Well, it ain't that much in parts and it won't get a lot cheaper than that.

    The only cheaper solution that immediately comes to mind is IF or RF
    chips for radios that have an RSSI output. But this will not be a linear
    function. If you are feeding this into something computerized it may not
    be a problem though.

    Since you are in NL Philips might be a good source for RSSI chips.

    Groetjes, Joerg
  13. Ken Smith

    Ken Smith Guest

    How about this:

    IN -----------! \
    ! \
    IN------------!+ \
    ! ---\---- Vcc
    ! !/c \
    ! ! \
    ! !\e /
    ! ----/-----+------
    ---!- / ! !
    ! ! / \ ---
    ! ! / / ---
    ! ! / \ !
    ! ! GND
  14. J.Koning

    J.Koning Guest

    Would you care for a few words of explanation?
    Thanks & rgds,
  15. Fred Bloggs

    Fred Bloggs Guest

    The Analog Devices Parametric Evaluation Tool goes berserk over that
    application. Here are other circuits you can consider:
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