virtual ground

Discussion in 'General Electronics Chat' started by haditya, Mar 2, 2006.

  1. haditya

    Thread Starter Senior Member

    Jan 19, 2004
    220
    0
    hi
    how does virtual ground get established.. is it there in all opamp applications? or only in ones using negative feedback(feedback frm output to invertin terminal)
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    It's only in inverting configurations. The junction between the input resistance and the feedback resistance is the virtual ground. The current through the input is cancelled by the opposite sign current through the feedback, so the inverting input is effectively at circuit ground potential.
     
  3. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    To add to Beenthere's explanation of virtual ground.

    In an opamp with negative feedback, the tendency of the opamp is to drive its output to a voltage that makes the voltage at the negative terminal equal to the voltage applied to its positive input terminal.

    The term "virtual ground" is mainly applicable when the opamp in question is configured as an inverting gain stage and is powered by a dual supply and the positive terminal is tied to ground. The tendency of the opamp is to adjust its output voltage as described above forcing its negative input terminal equal to zero volts. The negative terminal is then said to be at "virtual ground".

    hgmjr
     
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