Virtual ground

In circuit theory, a node may have any value of current or voltage but physical implementations of a virtual ground will have limitations in terms of current handling ability and a non-zero impedance which may have practical side effects.

A voltage divider, using two resistors, can be used to create a virtual ground node.

Since an operational amplifier has very high open-loop gain, the potential difference between its inputs tends to zero when a feedback network is implemented.

More precisely, it can be shown that the output voltage of the amplifier in the figure is approximately equal to

Thus, as far as the amplifier is working in its linear region (output not saturated, frequencies inside the range of the opamp), the voltage at the inverting input terminal remains constant with respect to the real ground, and independent from the loads to which the output may be connected.