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Kirchoff's current law question

  1. Sep 8, 2009 #1
    I'm looking at the derivation of a band pass filter circuit, and part of the circuit is a capacitor and resistor in parallel from the non-inverting input to the output. My thinking is that the current through the capacitor is going to be the current coming in (since the inverting input draws no current) minus the current going through the resistor, or Ic = I - Ir. Nope, the derivation has it the other way, Ic = Ir - I. I can't figure out why this is.
  2. jcsd
  3. Sep 8, 2009 #2
    depends on the standardization of current. If current is defined as direction holes travel in, than it follows passive sign convention whereas, current is usually defined as direction opposite of electron flow. I see your point. Ic + Ir = I so
    Ic = I - Ir...
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