Hi,
From your signal waveform it seems as you didn´t set V_COM at all.
--> Show us your circuit, with your voltages not a datasheet circuit.
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I personally don´t like the phrase "feedback" in this case. V_COM is an input to set the common mode voltage of the output signals.
It should be somewhere between the supply voltages, but not close to them.
I see no true "feedback".
All this should be explained in the datasheet.
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Often one uses a differential amp to feed a (high speed) ADC. If so, then often the ADC has a V_COM output. Connect it to the amplifier_V_COM input.
Klaus