vivkr
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Dear All,
Thanks for your comments.
Pancho: Thanks for the tip about gmbs and gds. I had forgotten those. gds is not a big issue, but gmbs is something I expected to have as 0 since I had shorted bulk and source together. As the DC operating point summary does not show gmbs, I did an XF analysis to estimate gmbs and gm, and very surprisingly, gmbs was nonzero. As a matter of fact, it was large enough to explain exactly the increased noise level. So, the issue seems to be resolved. I wonder why gmbs is nonzero though.
EDIT: A little thought to the matter suggests that gmbs does not need to be zero for zero bulk-source voltage, since this is basically a pn-junction diode, which will still respond to any AC signal (were there one present).
noimod=3 and I am using Cadence spectre so the SPICE2 model is used.
Best regards,
Vivek
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