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 Threshold voltage calculation 

Last post Fri, Dec 20 2013 1:17 AM by Andrew Beckett. 1 replies.
Started by aravindkvarier 21 Nov 2013 05:54 PM. Topic has 1 replies and 5228 views
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  • Thu, Nov 21 2013 5:54 PM

    Threshold voltage calculation Reply
    Sir, can you specify the steps required for calculating the exact threshold voltage of an NMOS device?
    • Post Points: 20
  • Fri, Dec 20 2013 1:17 AM

    Re: Threshold voltage calculation Reply

    What do you mean by the "exact threshold voltage"? Most devices output this as an operating point parameter - for example, if you do "spectre -h bsim4" you'll see a section labelled "Operating Point Parameters" and within that you have:

     Operating Point Parameters
    ==========================

    1       region=triode     Estimated operating region. Spectre outputs the number (0-4) in a rawfile. Possible values are
                              off, triode, sat, subth, and breakdown.
    ...
    9       vgb (V)           Gate-bulk voltage.
    10      vth (V)           Threshold voltage (alias=lv9).
    11      vdsat (V)         Drain-source saturation voltage (alias=lv10).
    12      gm (S)            Common-source transconductance (alias=lx7).
    13      gds (S)           Common-source output conductance (alias=lx8).
    14      gmbs (S)          Body-transconductance (alias=lx9).

    So if you do a DC operating point analysis (assuming you're using spectre, you didn't say) in ADE (again, you didn't say if you're using the Analog Design Environment), you can then do a Results->Print->Operating Point and click on the device in the schematic and look at the vth. Or you could annotate the operating point parameters on the schematic and by using the Edit->Component Display in the schematic or View->Annotation... menu (in IC616 onwards) you can choose what gets annotated.

    Whether the model's implementation of vth is what you're expecting or not by "exact threshold voltage" is another question!

    Regards,

    Andrew.

    • Post Points: 5
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Started by aravindkvarier at 21 Nov 2013 05:54 PM. Topic has 1 replies.