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TINA/Spice/LMH6881: single ended input impedance characteristics

Part Number: LMH6881
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

Hello,

I'm trying to simulate the single ended input impedance of the IC. We used Mentor System Vision and the TINA Spice model to export S-Parameters, the circuit is attached (s_param.png). We used a 50 ohm ac source and 2.5V offset for the common mode voltage. Afterwards I used the S-Parameter model to simulate the impedance inside another tool which I use for microstrip and filter desing. I used a 1A source and measured Vin which is propotional to Zin. I plotted the real and imaginary. (zin.png).

My plotted results look quite differently to the figure 36 from the datasheet (datasheet.png).

Where does this come from?

Can I trust the spice model?

Thank you.