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Working with DC sweeps and OP

MicheleA

Hi all,

I know it's not appealing to write one's first post in an RF focused group talking about DC but please bare with me :)

I am interested in plotting some MOS DC parameters like gm, gmoverid, Cgg, gds as they vary across VGS and VDS.

Keeping VDS fixed for the moment, I would expect to be able to DC sweep VGS and get a curve of - say - gm Vs. VGS. This is not the case. I actually get only one point, which is the point corresponding to the "static" value of VGS, in the design variables list.

Of course I could set up an equation in the Calculator for the derivative of Id but I think that "somewhere" the tool should calculate those parameters for me...And also because for some trickier parameters like Cgg the whole process would be more complicated.

The alternative to that is to run a parametric analysis, but this is way less effective timewise.

 Does anybody know of a way of overcoming this?

Thank you in advance,

 Michele

Parents

  • Thanks a lot Andrew!

    It works just perfectly. I could swear I also looked in the results browser but of course if gm is here now, it must have been there last time as well :)

    I have a second part for this question however :-D

    Now, to retrieve the behavior Vs. two variables, I have to do a parametric sweep (I suppose): DC sweep VGS, par sweep VDS. This means that my gm will become a bidimensional function...A surface in a three dimensional space. I don't think that the Visualization Tool  is equipped for plotting surfaces but actually what I need is plotting contours (slices of my surface).

    If there is a way of doing it in Cadence, I would be glad to learn it. If not, I guess I could export the data in tabular form.

    Can you point me to the place in the manuals where this topic is explained? I would also try to do it automatically, like more or less what you made me do for "save.scs"...Maybe include some "print.scs"?

    Thank you very much for your help,

     Michele

Reply

  • Thanks a lot Andrew!

    It works just perfectly. I could swear I also looked in the results browser but of course if gm is here now, it must have been there last time as well :)

    I have a second part for this question however :-D

    Now, to retrieve the behavior Vs. two variables, I have to do a parametric sweep (I suppose): DC sweep VGS, par sweep VDS. This means that my gm will become a bidimensional function...A surface in a three dimensional space. I don't think that the Visualization Tool  is equipped for plotting surfaces but actually what I need is plotting contours (slices of my surface).

    If there is a way of doing it in Cadence, I would be glad to learn it. If not, I guess I could export the data in tabular form.

    Can you point me to the place in the manuals where this topic is explained? I would also try to do it automatically, like more or less what you made me do for "save.scs"...Maybe include some "print.scs"?

    Thank you very much for your help,

     Michele

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