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Non Inverting Amplifier Currents

  1. May 19, 2013 #1
    I'm confused by the fact that for the typical non-inverting amplifier,
    op-amp_basic_non_inv.gif

    (1) The input current is ideally 0 A.
    but
    (2) The current going into ground is given by Vin/R1 where R1 is the resistor above ground.

    If Vin were provided by a battery for example, which has Voltage=0V on one side and Vin on the other doesn't this imply that the current isn't steady and charge is building up inside the battery?

    Thanks!
     
  2. jcsd
  3. May 19, 2013 #2

    mfb

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    Staff: Mentor

    The amplifier will draw the corresponding current from its power supply, which is not part of that sketch. No relevant charges are built up.
     
  4. May 20, 2013 #3

    NascentOxygen

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    Staff: Mentor

    The current through R1 has not come from the battery, and is not going to the battery. The amplifier input is high impedance, so practically no current is drawn from the battery, as you stated.

    As mfb indicated, current through the circuit components comes from/goes to the DC power supply powering the circuit (not marked in your schematic because everyone knows it's there anyway). :smile:
     
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