eldo_user

Setting Up An Analysis
Transient Noise Analysis
• When FMIN=0:
Noise sources are generated from random pulses.
See “Noise Sources Generated From Random Pulses” on page 247.
• When FMIN≠0:
Noise sources are generated from a sum of sinusoids.
See “Noise Sources Generated From a Sum of Sinusoids” on page 253.
Noise sources from random pulses have a continuous spectrum, whereas noise sources from
sinusoids have a discrete spectrum. Noise sources from random pulses are much faster to
generate than noise sources from sinusoids.
It is recommended to use noise sources from random pulses rather than from sinusoids
(FMIN=0). But in some cases, noise sources from sinusoids are useful, for example, when
specifying noise in a specific narrow noise bandwidth.
Noise Sources Generated From Random Pulses
When FMIN=0, for white noise sources, r(t) is generated using random pulse with a specific
width. The pulse magnitudes correspond to a random variable, with a Gaussian distribution and
a variance equal to 1. The pulse width is computed from the .NOISETRAN command parameter
FMAX (Tp=0.5/FMAX).
The m(t) part of the noise source is computed from the PSD of the noise model:
m(t)=sqrt(PSD(t) × FMAX)
As PSD is bias dependent, m(t) is instantaneously updated function of bias changes.
Eldo® User's Manual, 15.3 247