OPA2677: Driving a variable load without (or lowest) effect on the gain

Tool/software:

Hello,

I am using the OPA2677 to drive multiple twisted pair lines in parallel, resulting in a variable load. The input is a differential signal from a DAC with an output impedance of approximately 19Ω. I require a fixed gain between 1 and 2, with a bandwidth greater than 100MHz, and the circuit must operate with a single 12V supply.

It appears that the input impedance is matched using a balun, and both the gain and bandwidth meet the requirements. However, I have observed that the gain drops by approximately 2.5dB depending on the load value. Is there a way to reduce this dependency?

Best regards,

e2e.ti.com/.../TX_2D00_LineDriver.TSC