Stats

  • Locked Locked
  • Replies 1
  • Subscribers 125
  • Views 11795
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Model parameters clarity

shashwatss

Hello, I am a novice/student and have been using virtuoso since only about 3 months for designing DAC and current mirror biasing circuits. I have always used gm/Id methodology. Here, I would reference the x-axis to vdsat parameter to ensure corresponding biasing. I sadly cannot view a parameter called as Vov, as this could have been much more simpler, thus, allowing use of square law equations.

I would like to request if one may shed some helpful information regarding the following parameters so that I may be able to use virtuoso optimally:

  1. what are qsrco, qsi?
  2. difference between vgsteff, vdsat --> I made a plot between and it portrays a parabolic implying either bear higher order terms.
  3. difference between vdsat, vdss
  4. what is vgt?
  5. what is vsat_marg? The trend shows a drop an inverted characteristic to the better known vdsat,which can be understood, as the deeper the saturation, higher is vdsat. But vsat_marg bears an inverted trend?
  6. what is self_gain? Is it by chance related to gm/gds that allows choosing of optimum vdsat?

Thank you in advance

Regards,

Shashwat

  • Shashwat,

    I figured out that you must be talking about bsim3v3 models since some of these parameters only exist in bsim3v3. The first place you could look is to type: spectre -h bsim3v3 in a UNIX terminal, and then you'll see a section headed "Operating Point Parameters" (you should be able to enter:

    /Operating Point

    to search for that. This will give you a short description of the meaning of each operating point parameter.

    The next would be took in the bsim3v3 chapter of the Spectre Circuit Simulator Components and Device Models Reference which can be found in your Spectre installation - either by running `spectre_root`/bin/cdnshelp or just by looking at <SPECTREinstDir>/doc/spectremod/spectremod.pdf . This contains the same info (at the end of the chapter) but also all the equations. Unfortunately, whilst the bsim4 chapter has added links from the operating point parameters to relevant equations, this hasn't been done for bsim3v3 as that's not as commonly used for modern technologies as bsim4 - but it should give you some insight if they matter to you.

    Andrew.

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.