<Dd> V out V in = − R f R in (\ displaystyle (\ frac (V_ (\ text (out))) (V_ (\ text (in)))) = - (\ frac (R_ (\ text (f))) (R_ (\ text (in))))) </Dd> <P> An active virtual ground circuit is sometimes called a rail splitter . Such a circuit uses an op - amp or some other circuit element that has gain . Since an operational amplifier has very high open - loop gain, the potential difference between its inputs tend to zero when a feedback network is implemented . This means that the output supplies the inverting input (via the feedback network) with enough voltage to reduce the potential difference between the inputs to microvolts . More precisely, it can be shown that the output voltage of the amplifier in the figure is approximately equal to − R f R i n V i n (\ displaystyle - (\ frac (R_ (f)) (R_ (in))) V_ (in)). 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 output terminal remains constant with respect to the real ground, and independent from the loads to which it may be connected . This property characterize a "virtual ground". </P> <P> Voltage is a differential quantity, which appears between two points . In order to deal only with a voltage (an electrical potential) of a single point, the second point has to be connected to a reference point (ground). Usually, the power supply terminals serve as steady grounds; when the internal points of compound power sources are accessible, they can also serve as real grounds . </P> <P> If there are not accessible source internal points, external circuit points having steady voltage with respect to the source terminals can serve as artificial virtual grounds . Such a point has to have steady potential, which does not vary when a load is attached . </P>

Following is the basic property of virtual ground terminal of opamp