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)

 

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.

 

Originally posted by haditya@Mar 2 2006, 08:28 PM
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)

[post=14555]Quoted post[/post]​

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