As so many people said that hspice can't do the noise analysis of the fully differential amp,but i found that there is a .noise statement in the hspice manual,so what is the function of this statement.
And another question is that spectre can do the noise analysis of the fully differential amp?
SPICE can only do noise analysis on linear systems (including opamp), by the .noise system. For non-linear systems such as mixer, you can run spectre, by pnoise analysis.
Could you explain it in detail. Noise model is a seperate file or it's inclued in the process hspice model which is released by foundry.
And i didn't find the noise model information in hspice manual.
There are small differences between HSpice and Spectre regarding the linear noise analysis.
1. Spectre could use a voltage difference between two nodes as a noise output.
2. Spectre could use a specific DC analysis or an arbitary transient point as operating point for the noise analysis.
Hspice can do noise analysis only in AC analysis.
Spectre can do that in both transient and AC analysis.
Actually Spectre is better for noise analysis.
You can use .noise only after .ac analysis in Hspice.
.noise analysis ouputs the total input or output referred noise as you point the input and output node.
Hspice CAN do noise analysis for fully differential amp in AC analysis.