Hello,
I am running transient noise analysis in spectre. Upon adding the noise sources, the variance of total noise increases. But when I add some more transistors to the circuit with an intention to observe more noise (amplified) at a node, I actually do not see any effect as if noise is not being generated from the transistor sources but being generated from somewhere else and irrespective of the size of the circuit (also, noiseon parameter doesn't seem to be working). I already check all existing queries on Spectre transient noise analysis in cadence/eda forums and could not get any help from them. I will really appreciate your help on this. Pasting my transient simulation commands form the spectre netlist below:
Circuit is simple cross-coupled inverter. observing noise at Q (output node). And when I add additional circuitry (or transistors at Q node, the noise should increase, right?)
simulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=50.0 tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" checklimitdest=psf
tran tran stop=100p errpreset=moderate method=trap noisefmax=500G noiseseed=1862 noisescale=1 write="spectre.ic" writefinal="spectre.fc" annotate=status maxiters=5
finalTimeOP info what=oppoint where=rawfile
modelParameter info what=models where=rawfile
element info what=inst where=rawfile
outputParameter info what=output where=rawfile
designParamVals info what=parameters where=rawfile
primitives info what=primitives where=rawfile
subckts info what=subckts where=rawfile
Model file comands for noise below: (model file is from ptm asu 16nm lstp : http://ptm.asu.edu/modelcard/PTM-MG/modelfiles/lstp/16nfet.pm. http://ptm.asu.edu/modelcard/PTM-MG/modelfiles/lstp/16pfet.pm. )
************************************************************
* noise *
************************************************************
+ef = 1
*========================== 1/f ===========================*
+lintnoi = 0 em = 41000000 noia = 6.25e+039 noib = 3.125e+024
+noic = 87500000 ntnoi = 1 tnoimod = 0
Thanks!