Editing Virtual ground (section)

==Construction==
A [[voltage divider]], using two resistors, can be used to create a virtual ground node. If two voltage sources are connected in series with two resistors, it can be shown that the midpoint becomes a virtual ground if

:<math> \frac{V_\text{out}}{V_\text{in}} = -\frac{R_\text{f}}{R_\text{in}} </math>
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[[Image:opampinverting.svg|right|thumb|280px|Op-amp inverting amplifier]]
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 tends 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 <math>-\frac{R_f}{R_{in}} V_{in}</math>. 
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. 
This property is characterized a "virtual ground".