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Homework Help: Virtual Ground

  1. Sep 14, 2009 #1
    What is the principle of virtual ground? Please elaborate.
    The input impedance of an op-amp is so high that virtually all input current is shunted to the feedback resistor when is works as interver. When noninverting input is grounded and internal resistance of op-amp is very high, then due to no potential drop the inverting input is also grounded and this is called virtual ground.
  2. jcsd
  3. Sep 15, 2009 #2


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    In these feedback circuits, the op-amp adjusts the output voltage in such a way as to keep the inverting input (-) at or close to ground potential.

    However, current cannot actually flow into (-) to ground. That's why it's referred to as a virtual ground.
    Last edited: Sep 15, 2009
  4. Sep 15, 2009 #3


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    The op-amp attempts to force its inputs to the same voltage. If one input is grounded (i.e. held at 0V), the op-amp will force the other input to also be grounded. It's virtual because you cannot source or sink current from it; the op-amp inputs have very high impedance.

    The "virtual ground" principle is really just a special case of the "virtual short" principle.

    - Warren
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