manodipan wrote on Oct 1st, 2008, 2:16am:By the awy i have heard some term like transient noise simulation,what is that??
Spice's "noise" is a small-signal analysis, like ac: the circuit is linearized about an operating point to compute the transfer function from the noise generators to the output.
PNoise goes a step further and computes a "time-varying operating point" but again linearizes the circuit. Similar for HBnoise.
Transient noise does a regular transient analysis, but then uses the noise equations to inject random amounts of charge (or voltage) and attempts to compute the full nonlinear response in the presence of noise. I think there's a whitepaper on SourceLink. It's really the only way to get the noise performance of sigma-delta converters (and other circuits that aren't periodic nor linear). But it's tricky to not lose the noise in the numerical roundoff of finite-precision computer arithmetic, and to have good convergence in the presence of the random noise.