I am trying to construct an amplifier circuit using a fully differential op amp (THS4503) to interface with an ADC (ADS5232). I will be reading a 0-5V sensor, which needs to be converted to a 1Vpp differential signal. I have the circuit constructed according to the datasheets of the respective components along with the help of a TI app note (sloa054e.pdf) (p.17-19), since my sensor requires a 50 ohm termination. I'm simulating the circuit in LTSpice using models created by TI for the amplifiers. When I sweep the input voltage, I am getting some weird nonlinearities at the end of the range, and I'm not sure how to resolve it. I checked the datasheets and I am within the voltage swing of the amp, and I checked current flowing through the components and I am within the current rating of the amp. Plus, it doesn't quite make sense, since the amp is able to provide the same voltages at the beginning of the input range, just not at the end.
Thank you for your help!