I tried adding a model to one of the standard.jft located at C:\Program Files\LTC\LTspiceXVII\lib\cmp (actually I was updating the standard.jft files from LT spice wiki, if you haven't done this you should check it out). But I get no change when loading LTspice XVII when I look for the models in the drop down list of the Jfet. How do I add a model to the standard model files in LTspice XVII?

  • \$\begingroup\$ In the past when I updated the standard.* files with new part models, I had to close LTspice and then restart it. It would then reload those files. It also used to, during updates, preserve my additions while adding its own during the update. So the updating process was pretty fancy, actually. Anyway, the parts just showed up in the list. \$\endgroup\$
    – jonk
    Commented Jan 19, 2018 at 23:34
  • \$\begingroup\$ You can also add a whole bunch of models to any of your own .LIB or .MOD files referenced by a .ASC and you can get a specialized drop down from LTspice that lists out exactly those part numbers you have included in your own LIB/MOD file. That's also nice. \$\endgroup\$
    – jonk
    Commented Jan 19, 2018 at 23:35
  • \$\begingroup\$ As a new user Library maintenance in LTSPICE is one the things I am having the hardest time with. I'm surprised at not being able to find any simple little third part tools that let you simply drag and drop files into the library automatically. \$\endgroup\$
    – Trevor_G
    Commented Jan 20, 2018 at 1:43
  • \$\begingroup\$ @jonk I'll have to try that, that would be useful Thanks \$\endgroup\$
    – Voltage Spike
    Commented Jan 20, 2018 at 5:20
  • \$\begingroup\$ forgive me if I'm statong the obvious, but you must relaunch ltspice. \$\endgroup\$
    – dim
    Commented Jan 20, 2018 at 7:40

2 Answers 2


There are now two folders, one is the standard folder at


The other folder is in (on a windows machine)

..\\My Documents\LTspiceXVII\lib\cmp

if you change standard.jft (or .jft .bjt .dio .cap) at the above location it will be reflected in the drop down menu.

  • \$\begingroup\$ I also use a special Doc* directory for LTspice, just as you did. Windows hates it when you edit the program files directories. So it is easier to just add stuff in the documents folder where permission problems "go away." \$\endgroup\$
    – jonk
    Commented Jan 19, 2018 at 23:39
  • 1
    \$\begingroup\$ Yeah, I guess that was nice from that perspective. There were a few moments when I was changing standard.jft and the changes wern't going through, I was about to throw my computer across the room, and then I found that directory. \$\endgroup\$
    – Voltage Spike
    Commented Jan 20, 2018 at 5:23

In ...\LTC\LTspiceXVII, you'll find an executable file called "UnLink". Run it. It will unlink your installation files.

Now, run XVIIx64 or XVIIx86 (whatever suits your hardware). It ask you to update LTSpice. Click "Yes". It will initiate installation of all files and libraries from scratch. Once this is done, you'll find the SPICE models located in the updated .jft/.bjt/.dio/.cap/.res file.

Let me know if this works.


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