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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

  •  Dear Andrew,

    i've a very similar problem. But following your suggestions I get the data I looked for.

    Instead of running a spectre script from the shell, I use OCEAN. Is there a direct way to insert the "save Mx:oppoint" statement directly in the ocean script, w/o including this ASCII file in the include lib statement?

    thanks a lot for your valuable support.

    Josef

     

     

  • Josef,

    The forum guidelines suggest not posting a question in more than one forum and also not appending to old threads (in general).

    So I will answer this via your other post.

    Andrew.

  • Hello, I would like to do the same thing: plotting the gm after a dc sweep, but I can't get the plot. In my case, I want the gm of the instance M1, contained in instance I2. Below the steps I followed:

    -  create ASCII file called "save.scs", where I put the following line:     save I2/M1:oppoint

    - add "save.scs" in Setup->Model Libraries in ADE

    - run dc sweep

    - in ADE: Tools->Results Browser

    - open the calculator and type:     getData("I2/M1:gm" ?result 'dc)

    In CDS.log, I get:   expression evaluation failed: getData("I2/M1:gm" ?result 'dc)

    What am I doing wrong?

    Thanks!!!!

  • You're mixing delimiters. You need to use simulator names, so it should be getData("I2.M1:gm" ?result 'dc)

    Regards,

    Andrew.

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