Virtual Ground on operation amplifiers
Single-supply operation requires the generation of a virtual ground, usually at a voltage equal to Vcc/2. The circuit in Figure 2 can be used to generate Vcc/2, but its performance deteriorates at low frequencies.
R1 and R2 are equal values, selected with power consumption vs allowable noise in mind. Capacitor C1 forms a low-pass filter to eliminate conducted noise on the voltage rail. Some applications can omit the buffer op amp. In what follows, there are a few circuits in which a virtual ground has to be introduced with two resistors within the circuit because one virtual ground is not suitable. In these instances, the resistors should be 100 kW or greater; when such a case arises, values are indicated on the schematic.
#From Application Report of Texas Instruments