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Adding Flicker noise parameter to resistor model

jdp721

Hi,

I am trying to run the simple example as depicted in the attached image, taken from Cadence's "Application Notes on Direct Time-Domain Noise Analysis using Virtuoso Spectre" document.

But, I am not able to implement the resistor (with the user defined parameter kf) as required here! For this, I tried to take a "res" from analogLib, and then change its "model name" to say "flickres_jdp" and also made a model file (say flickres_jdp.scs) - then added this model file from ADE->Setup->Model Path. The text put in this model file is:

simulator lang = spectre

model flickres_jdp resistor rsh=1k kf=10e-13

I am getting error of following type whenever the parameter kf is set to any non-zero value:

ERROR (SPECTRE-16384): Signal V(vout) = -2.45831 GV exceeds the blowup limit for the quantity `V' which is (1 GV)....Analysis `tran' was terminated prematurely

Can anyone please point the mistake that I am doing causing the sim to fail?

  • From a quick discussion with R&D on this, we suspect that the issue is that the flicker noise ends up with a fairly large amplitude (I found the blowup is also dependent upon how wide a bandwidth your noisefmin and noisefmax covers, and the duration of the simulation too), and then that causes the overall drop across the resistor to increase, which causes the flicker noise to increase further and so on - until it blows up. So there's some kind of numerical instability in there. If you have a voltage source across the resistor rather than a current source, it doesn't happen either.

    My suspicion is that the problem would only happen with a trivially simple circuit such as this when using ideal current sources. Probably in real circuits it would be OK. If you find otherwise, please contact customer support and we can look into it properly.

    Regards,

    Andrew.

  • Thank you Andrew for your helpful reply :)

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