Hi, anyone know how can I simulate Phase Noise in ngspice ?

Unfortunately, there is no large-signal noise simulation in

ngspice

, so you can’t really simulate it (at least out of the box, with some hacking maybe you can).

what is that about hacking?

Means: Try to estimate voltage or current noise contributions from resistors and MOSFET, and model them by adding voltage/current sources that support transient noise (available in

ngspice

). I never tried that myself, but theoretically should work. Resistors are easy to model as thermal noise is not a function of operating point, MOSFET are tricky because it is. When the operating point is not changing much that should be relatively close to what happens in the real world. This would be my approach to simulate transient noise behaviour of a circuit given that the open-source simulators lack this capability. Maybe @Boris Murmann has further ideas.

I don't have any good ideas to add.