I'm trying to insert a white noise in a LNA description but it is always null.

Here is the way I'm trying to insert the noise:

V(Noise) <+ white_noise(4*$temperature, "white noise");

Or something else with many other variations: constants, variables, etc, in the white_noise command.

The value when I simulate is always zero. Someone could help me generating an white noise?

Hello Brenox,
Are you trying to add noise to a Verilog-AMS model for transient simulations?  If so, you can create a noise generator model to inject voltage or current noise in a model.  Doing so is quite useful for exploring noise propagation in nonlinear systems such as RF mixers, switched-capacitor filters or delta-sigma A/D converters.

The key is to create a pseudo-random stream of real numbers at a sample rate much higher (about 20x higher) than the maximum frequency of interest.  You may then filter that stream as desired, then scale and assign it to a voltage or current.

You may contact me directly for more details or clarification.

Cheers,

Bob Peruzzi
www.RPeruzzi.com