I am running a SPICE simulation (in Altium Designer) using the supplied model for the ADA4857. If I load the output of the amplifier with anything less than 1Meg or so the output sags very significantly - but I get reasonable performance with a 1Meg load. In the data sheet it mentions performance into a 1K load. I am down 20dB when I drive a 1K load. I have checked and double checked my connections and everything looks correct. Suggestions of what might be wrong or how to go about troubleshooting this issue would be most welcome. Thanks!