Need some help..

Discussion in 'The Projects Forum' started by muralirmd, Jan 4, 2009.

  1. muralirmd

    Thread Starter New Member

    Jan 4, 2009
    1
    0
    Hi.
    Im new to this forum and it is nice..I need a circuit of R/2R ladder with 36 nodes..voltage level is (0-3v).I have tried a lot but not able to get this circuit..Help me please..
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    http://en.wikipedia.org/wiki/Resistor_Ladder

    If you're wanting 36 bits of precision, you won't get there. As far as DACs go, 10 bits is very common, 12 somewhat less common. 16 bit DACs are available.

    You'd be hard-pressed to build an accurate DAC with more than 12 bits from discrete components.
     
  3. hgmjr

    Moderator

    Jan 28, 2005
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    I agree with sgtwookie. The precision limitation of the components available to implement a 36 bit D-to-A would easily negate any benefits to be gained by going to such an extreme. I have encountered some 16-bit D-to-A convertors but 12 bits seems to be a practical lower limit for such designs.

    hgmjr
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    I worked for an outfit that made 25 bit R/2R A to D converters. The .01% resistors all from the same lot of resistance wire were a bit costly. Matching the conduction of each set of switching diodes was critical and tedious.

    36 bits would not be attainable, as the lowest few bits would be unresolvable, due to being down in the quantum noise. Not too sure the R/2R ladder values would be possible.
     
  5. italo

    New Member

    Nov 20, 2005
    205
    1
    BOBODY EVER HEARD OF DUAL RAMPS CONVERTERS YET?
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Maybe I misinterpreted our OP - perhaps he wanted 36 discrete steps, which would be 6 bits? :confused: In that case, the link I posted shows a 5-bit R2/R ladder... adding one more pair would do it.
     
  7. hgmjr

    Moderator

    Jan 28, 2005
    9,030
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    Hopefully the OP will return and provide us with a much needed clarification.

    Are you looking for 1 part in 68,719,476,735 or are you looking for 1 part in 36?

    hgmjr
     
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