eldo_user

Setting Up An Analysis
Noise Analyses
Noise Analyses
The noise related analyses are:
• “Noise Analysis” on page 239.
• “Transient Noise Analysis” on page 241
• Eldo RF Steady-State Noise Analysis, see “RF Analyses” on page 283.
Noise Analysis
The .NOISE command specifies a noise analysis, which is performed in conjunction with the
small-signal analysis. The circuit is linearized around its DC operating point, and the
contribution of all noise sources is summed at a given output. All node voltages and currents are
assumed to be small sinusoidal signals, all at the same frequency.
The noise generated by devices is usually modeled as an equivalent noise spectral density,
which is a frequency-dependent function. Thermal noise, shot noise and flicker noise are all
noise sources due to different physical mechanisms, but they can be modeled as noise spectral
densities, enabling the computation of how much noise (as an RMS voltage) a device generates
in a given bandwidth.
Use the NONOISE parameter on a device model or instance to specify that no noise model will
be used for the device when performing noise analysis. The device presents no noise
contribution to the noise analysis.
Noise Analysis Results
Noise results can be sorted in different ways with the .OPTNOISE command.
Example noise results:
******** NOISE IN THE DOMAIN 1.000000E+002Hz 1.000000E+004Hz ********
OUTPUT NOISE PER DEVICE :
R8 : 2.45421E-011 V^2 ---> : 4.95400E-006 V
R12 : 2.09786E-011 V^2 ---> : 4.58024E-006 V
R11 : 1.86080E-011 V^2 ---> : 4.31370E-006 V
R9 : 9.84669E-012 V^2 ---> : 3.13794E-006 V
R10 : 4.74119E-012 V^2 ---> : 2.17743E-006 V
R2 : 2.03321E-012 V^2 ---> : 1.42591E-006 V
R6 : 1.69155E-012 V^2 ---> : 1.30060E-006 V
R5 : 6.59705E-013 V^2 ---> : 8.12222E-007 V
R4 : 5.86775E-013 V^2 ---> : 7.66012E-007 V
R3 : 3.27669E-013 V^2 ---> : 5.72424E-007 V
R1 : 2.04526E-013 V^2 ---> : 4.52246E-007 V
R7 : 2.02087E-013 V^2 ---> : 4.49541E-007 V
TOTAL OUTPUT NOISE 9.188156E-006 Volts
Eldo® User's Manual, 15.3 239