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  3. dcOp sweep

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dcOp sweep

drdanmc
drdanmc over 8 years ago

I'm interested in being able to *quickly* simulate some device small signal characteristics versus some parameter (design variable, temperature, etc).  A dc sweep with dc operating point enabled in ADE-L (or even just straight up spectre from the command line) only reports dc operating points (like gm, gds, etc) at the start point.  I've enabled saving as much as I can in the Save All area.  A careful inspection of 'spectre -h dc' would seem to imply that indeed you can't save off operating points as part of a dc parameter sweep.

I can do a parametric analysis, but the overhead of spectre starting and loading the netlist each time is pretty awful.

I can use a 'sweep' analysis in spectre and if I'm in ADE-L I can play games with puttting the 'sweep' analysis in a model file that gets included.  But... then when it comes to results, each point shows up as a single analysis and I don't have a clean way to combine them all unless I write some ocean code to dig through each but that seems like a hack.

If I just put together some loops in ocean, it looks like spectre is indeed running in interactive mode (batch would be even slower).   However, I'm seeing something like 2.5 seconds per point with an ocean script which quite frankly stinks for a circuit with 1 transistor.  I should be able to run 1000 points in a few seconds (or less) instead of almost an hour.

It may be that my best choice is a nested set of 'sweep' runs in a command line spectre and then use python to grab out data from the spectre logfile.  Surely there should be a better (faster) way?  Spectre has the underlying horsepower to where this should be a nothing sort of job.  I suppose another alternative is to use python to generate a really big netlist with all of my operating points which may be a few thousand, and just get them all at once in parallel.  

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  • Andrew Beckett
    Andrew Beckett over 8 years ago

    Unknown said:
    Thanks yet again for your help Andrew.  Regarding the 2.5s in interactive mode, I can send in something although this is a pretty long standing thing for as long as I can remember (back to IC 4.3 or 4.4 days).

    Please do Dan; it really shouldn't be this bad.

    Andrew.

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  • Andrew Beckett
    Andrew Beckett over 8 years ago

    Unknown said:
    Thanks yet again for your help Andrew.  Regarding the 2.5s in interactive mode, I can send in something although this is a pretty long standing thing for as long as I can remember (back to IC 4.3 or 4.4 days).

    Please do Dan; it really shouldn't be this bad.

    Andrew.

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