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Homework Help: Digital-Analogic conversion help

  1. Oct 16, 2006 #1
    I'm trying to work out an equation for the circuit below,but unfortunately I'm not having success.I've managed to get the expression for I1 which is:

    I1=(Vin)/2R

    How do I find now the expression for I2?Following the equation V=RxI where V is the difference at both terminals of the resistance I need to find the value tension at point A.How do I find that value?I've found the parallel resistance between the resistances that correspond to currents I3 and I4 which is R by I don't know how to work it from that!:confused:
    Any help is really appreciated!Thanks in advance!

    http://i75.photobucket.com/albums/i281/esmeco/digitalanalogicconverter.jpg
     
  2. jcsd
  3. Oct 17, 2006 #2

    berkeman

    User Avatar

    Staff: Mentor

    Two things. First, the simulation schematic looks like it has a couple connection errors in it. The bottom of the + input network is not connected to the - input network side or to a "ground" symbol as far as I can see. Is something missing?

    Second, the trick with R:2R ladders is to see that in a ladder, the R is in series with a 2R in parallel with a net 2R. That gives you a consistent voltage divider characteristic that you can use in a DAC ladder. You might see if wikipedia or your textbook describes the R 2R ladder to get a better explanation. Hope that helps some.
     
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