You can use the HFA1212 dual video buffer to implement differential line drivers and receivers (Fig 1) with a minimum of external components. Common-mode rejection is a function of the internal matched thin-film resistors, which you can pin-strap to set the required loop gains. V_IN terminates in 75ê and drives both amplifiers in IC₁. IC_1A and IC_1B have gains of -1 and +1, respectively. These amplifiers create a differential signal with a net gain of two. The 75(ohm) series resistors at the outputs provide impedance matching to the transmission line.

The 150(ohm) resistor on the receiver side of the transmission line provides proper impedance matching and attenuation for a gain of one at the receiver input. IC₂ performs differential-to-single-ended conversion and provides common-mode rejection. IC_2A is configured for a gain of +2. IC_2B subtracts common-mode signals and provides a gain of +2 to differential signals. When V_OUT terminates in 75(ohm), the overall gain from V_IN to V_OUT is unity. Because of the gain of +2 in IC_2A, the peak voltage at the receiver may not exceed 1.5V.

The oscilloscope photo in Fig 2 shows the common-mode rejection of the receiver. V_IN is a 10-MHz, 1.5V p-p sine wave. A 1-MHz, 1.5V p-p common-mode signal drives the ground reference of Fig 1's IC₁ (with respect to the ground of IC₂). The upper trace shows the combined signal that appears at R_X-. V_OUT, seen in the bottom trace, is a faithful reproduction of V_IN, with the common-mode signal removed. (DI #1709)