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idea about differential circuit

Discussion in 'Electronic Design' started by [email protected], Sep 7, 2007.

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  1. Guest

    Is there a way to build a two-way differential circuit i.e. a circuit
    that compares a varying voltage to a reference, and if that voltage is
    rising, it gives a certain value (say 1), while if its decreasing, it
    gives 0. I was thinking of using a quad comparator but is there a
    simpler solution? TIA
  2. Guest

    Would this be what you're looking for?
    Without more info, this is what popped to mind.
  3. Joel Kolstad

    Joel Kolstad Guest

    How about: Take a capacitor, connector one side to your signal (assumed to be
    low impedance), the other side to a small resistor. Size the resistor and
    capacitor such that the reactance is much greater than the resistance (in
    general, this means a rather small R). The idea is that the circuit looks
    like just a capacitor to the input, so I is still very near equal to C*dv/dt,
    but you generate an output voltage across the resistor (Vres=C*dv/dt*R) which
    is the derivative of the input signal. The sign of that voltage tells you is
    the voltage is rising our falling -- use a single comparator to "square it up"
    if you need to.

    You'll probably also need a bit of filtering/hysteresis in the system so that
    noise doesn't cause the output to oscillate wildly when the input signal is
  4. Dleer

    Dleer Guest

    you need a simple "window" comparator circuit, 2 comparators and some
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