I would like to add some new components to the LTspice library. I have never done this before.

The online SPICE forum discusses 3rd party component steps. It says I have to download the SPICE model file from the manufacturer's website. I have tried to find the SPICE model file for the FDA69N25 MOSFET from Fairchild, but I can't seem to find the specific data clip.

There is the datasheet and other info regarding the packaging, but I just can't make heads or tails of the other export files. I don't know which should be the SPICE model file.

From what I have seen, if you know what you are doing it is quite easy to import the right component into LTspice, but I don't quite have enough experience with the simulator.


1 Answer 1


If you have the file, its a text file, usually cir/txt/lib extension. You should see a standard header somewhere in the file (after comments): It looks like this .subckt XXX 1 2 4

XXX should say something like FDA69N25 or FDA69N

I couldn't find the file on their site, I would request it from a manufacturer. If you can't do that you'd have to try and create your own or find a similar transistor that has a spice file.

Here are the instructions for import: https://www.analog.com/en/technical-articles/ltspice-simple-steps-to-import-third-party-models.html

  • 3
    \$\begingroup\$ The similar FQA62N25C is provided with a SPICE model on the manufacturer's site. I'd use that as a starting point and try to adjust the model to match \$\endgroup\$
    – jms
    Commented Jan 5 at 22:20
  • 2
    \$\begingroup\$ Another reference that's useful for things like transistors is this one: analog.com/en/technical-articles/… \$\endgroup\$
    – Ste Kulov
    Commented Jan 6 at 0:01
  • \$\begingroup\$ I got to download the file for the FQA62N25C (it is similar in design indeed), and changed the paramaters for an LTspice existing diode. I also got to write that file into the library file of LTspice, though the symbol fits the pin specifications written on the site of the manufacturer. From what I have searched online, I can change the symbol by importing a mosfet file from file explorer. I tried to do the same thing for the 1n4007 diode in the SPICE instruction steps video, but after I searched for the respective diode directly into LTspice.... \$\endgroup\$
    – David Ab
    Commented Jan 6 at 18:15
  • \$\begingroup\$ .....I can see that the diode exists on the local directory (therefore, also on the library file), but when I want to use that diode and select it from the list of components, I get another diode, or at least one with a different name. For example: instead of d 1N4007 I get d 1SS294. Why is that? Is as if the information for the diode exists internally, but there isn't an available component, or perhaps symbol that allows me to use it. I created a symbol for the mosfet when I downloaded its files, so perhaps I have to do the same thing? Do I need to create a new symbol so as to use the diode? \$\endgroup\$
    – David Ab
    Commented Jan 6 at 18:20
  • \$\begingroup\$ From what I see, LTspice doesn't allow me to file a symbol for the 1n4007, so I wonder what is there to be done? \$\endgroup\$
    – David Ab
    Commented Jan 6 at 18:23

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