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Digital to analog converters

  1. Jul 9, 2015 #1
    1. The problem statement, all variables and given/known data
    The input bits 0 and 1 are represented by 0 volts and 5 volts respectively. The OP-AMP is ideal, but all the resistances and the 5 volts inputs have a tolerance o f ± 10%. The specification (rounded to the nearest multiple of 5%) for the tolerance of the DAC is??
    In this question all I want to know is what is the physical significance of the term tolerance as given for the resistor , what's the purpose?? And we have to find tolerance of dac , what does this mean??

    2. Relevant equations
    In the solution , they found out the output voltage of op-amp and put the values of the individual tolerances..how they got to know that we have to find output voltage's tolerance from the given problem??
    Voutput = -Vr [Rf/R] where Vr is the reference voltage



    3. The attempt at a solution
     

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  3. Jul 9, 2015 #2

    Hesch

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    Gold Member

    No resistors are exact. Say ( in this example ) that you have bought a resistor marked with the colors:
    brown - black - orange - silver :
    It means that this resistor is specified: 10 * 103Ω ± 10%

    The shown DAC doesn't care about the voltages connected to the inputs, but about the currents flowing in the resistors: I = V / R. So if a connected voltage to some input is 10% too high, and that the resistor for the same input is 10% too small, what will the resulting output from the DAC be, as compared to the ideal output, due to this input?
     
  4. Jul 9, 2015 #3

    rude man

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    Confusing post.

    Only thing I can figure out is you want to know the error band in the op amp's output given 10% tolerance on the 5V inputs and the resistors?

    In which case, how do errors propagate when the output is a product of three parameters (2 resistors & 1 input voltage), all assumed independent of each other and normally distributed?
     
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