eldo_user

Setting Up An Analysis
Transient Noise Analysis
FMIN and FMAX. It means that the generated noise sources have a spectrum of discrete points
and the energy of the noise sources is localized in a limited number of frequency points. When a
frequency band is wide the corresponding generated noise source may have a poor frequency
resolution.
Consequently, an alternative algorithm was developed to generate the noise sources, leading to
a continuous spectrum in the frequency band zero to FMAX. This algorithm is approximately
twice as fast and with more accurate results. However, it cannot generate a noise source with a
frequency band beginning at a value of FMIN other than zero. This algorithm is automatically
activated by specifying FMIN as zero. When FMIN is not zero, the method using sinusoids is
then used. Both methods can work together, one for some components, the other method for
different noisy devices.
The alternative method (when FMIN=0) is used to generate flicker noise and white noise
sources (thermal and shot noise). It is not possible to have a flicker noise source with a
frequency band starting from zero, therefore the generated flicker noise source will have a white
spectrum from zero to f1 and a flicker noise spectrum from f1 to FMAX. The frequency f1 is
calculated from the transient simulation duration: f1=1/TSTOP.
Related Commands
• .NOISETRAN command in Eldo Reference Manual
• .TRAN command in Eldo Reference Manual
Related Topics
Generation of Time Domain Noise Sources
Generation of Time Domain Noise Sources
During noisy runs, each noise source is represented by a current or a voltage source. This source
is pseudo-random and its characteristic is computed from the PSD model of the noise source. As
the noise PSD models might depend on the device bias, and as the device bias is time varying
during a transient simulation, the characteristics of the sources are updated function of the
instantaneous device bias.
A time domain noise source n(t) is generated with the following form:
n(t) = m(t) . r(t)
Where m(t) is a deterministic modulation part, calculated from the instantaneous bias conditions
of the corresponding noisy device, and r(t) is a stationary random part that also contains the
frequency dependence of the noise source.
There exists two different ways to generate noise sources inside Eldo. The choice of the method
is triggered by the FMIN parameter of the .NOISETRAN command.
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Eldo® User's Manual, 15.3