Figure 79 shows a differential amplifier that is used to amplify differential signals to a differential output. This circuit has high input impedance and is used in differential line driver applications where the signal source is a high-impedance driver (for example, a differential DAC) that must drive a line.
The output of the amplifier can be calculated according to Equation 11 if VIN± is set to VCM + VSIG±.
The signal gain of the circuit is shown in Equation 12, and VCM passes with unity gain. The amplifier combines two noninverting amplifiers into one differential amplifier that shares the RG resistor, which makes RG effectively half its value when calculating the gain. The output signals are in-phase with the input signals.