Optimum Resistance for low noise figure

Nevermind, delete please

Haven't used LTSpice,  how does it calculate noise figure,  is it accurate? Note : Noise figure is not output voltage noise, but rather the degradation of S/N radio.  And is the OPA134 model that detailed to determine optimum source impedance?

You generally don't want to add series resistance to match things as the resistor itself then contributes  noise. The optimum way is with a complex conjugate (reactive) match.

As far as I am aware, none of the models in spice accounts for noise other than resistance.

In other words it only models Johnson noise.

Cheers

Ian

Actually some models include noise voltage density and noise current density. I believe all the models included in the default library include the noise data. Third-party models may or may not include these data. You have to try and check how noise changes with source impedance, see if it follows Johnson only or if the current density shifts the result.