SOAtherm-NMOS symbol missing in LTspice XVII

I am trying to follow the tutorial for Modeling Safe Operating Area Behavior of N-Channel MOSFETs (, but LTspice XVII does not have the SOAtherm-NMOS symbol that is used in the tutorial.

  • 0
    •  Analog Employees 
    on Feb 15, 2019 4:08 PM over 2 years ago


    I have LTspice XVII installed on my PC, and it's available for me:

  • It's definitely not there for me. I also just updated after seeing that you have it and it's still not there.

  • 0
    •  Analog Employees 
    on Feb 15, 2019 4:43 PM over 2 years ago in reply to jgavin

    Interesting.  I purged LTspice from my PC, and reinstalled, and now seeing that the model is missing.  I'll report this, and let you know when it's resolved.


  • 0
    •  Analog Employees 
    on Feb 15, 2019 7:54 PM over 2 years ago

    jgavin - I've been informed that the SOAtherm-NMOS symbol has been obsoleted, and this functionality now works without needing that symbol.

    See SOAtherm-Tutorial.asc in the examples/educational directory

  • 0
    •  Super User 
    on Feb 15, 2019 8:04 PM over 2 years ago


    The symbol SOAtherm-nmos.asy has been removed.

    Excerpt from the file changelog.txt : 01/18/19 Removed the obsoleted SOA accounting files from new installations.

    If you had installed LTspiceXVII before this date, the symbol is still t here, because LTspice hasn't removed it in the newer version.

    Even if you still have this out-dated symbol, you can't use it anymore, because the model-file belonging to this symbol has been removed by the later versions of LTspiceXVII.

    In the old way of SOAterm, a subcircuit has been used for this model in the simulation. I guees it had increased the simulation time too much. 

    The new method of SOAtherm:

    First I recommend to run the example from the folder Examples.


    When the simulation of this example has finished, it plots tj#q1 and tc#q1.
    The default ambient temperature is 85°C. You can change the assumed ambient temperature with the procedure below.

    CTRL-right-mouse-click on the Mosfet -> a dialog box will appear
    Enter in SpiceLine   Tambient=50
    Click on "Vis"in this line, if you want make this parameter visible in the schematic

    VDMOS-models which have thermal parameters can be identified by looking for the parameter "Rtheta" in its VDMOS model. Only a small percentage of the models have thermal data. The thermal calculations are only done if the following SPICE-directive is in the schematic.

    .options SOAaccounting=1