Hi Aliaksandr, Can you make your sim project public so we can inspect the spice netlist? Thanks.

You can only run sims using parts from the System > Spice libraries. Simulatable symbols are darker blue and have a small "S" in them when viewed in the Search Libraries tool. I think what is wrong is that you have used a symbol from the **System** library and not from the **System > Spice Discrete **library   * Please see: [https://easyeda.com/andyfierman/2n7002_d-test](https://easyeda.com/andyfierman/2n7002_d-test)

Great thanks! Your approach with searching in System library really works. But finally I see about 100 elements in Spice Discrete space. What about if I need some mosfet which is not in the list? For instance BF250. I found its spice model but still cannot apply it to simulation. I made my project public but not sure how I can share it with you. Here the link: [https://easyeda.com/editor#id=c91210bbb5c44a12982dad84bf66b365](https://easyeda.com/editor#id=c91210bbb5c44a12982dad84bf66b365) Project name is VeniceLights Thank you in advance!

"What about if I need some mosfet which is not in the list? For instance BF250. I found its spice model but still cannot apply it to simulation. " That is explained in the SImulation Tutorial. In fact you did everything right excpe that you started with a nonsimulation Schematic Symbol instead of a Spice Symbol from the Spice library. All you need to do is place the spice symbol in your sim, then if you want to use a different model do exactly what you did in your original sim. Paste the model into the schematic (or a separate sheet in the same project), chenge the name ofthe symbolin the schematic to theexact name of the new model and lastly, check the symbol to see if the spice prefix needs to be changed (M for a .model defined MOSFET model or X for a .subckt defined MOSFET model). It's worth checking the spice pin numbering but they are usually all the same DGS 123 sequence. Where it may go wrong is if the model is not SPICE3 or SP3 compatible. Pspice models may use a different syntax for some things so the models may have to be edited to get them to work in Ngspice. This problem will go away when we swap to using LTspice as the simulation engine. most 3rd party models will "just work" then. It does mean I have to undo a lot of ngspice specific tricks in many of our in-house models but that's life... :)

If you look at your spice netlist, you'll see that there is no Q1.  That's because the spice netlister doesn't see the mosfet symbol because it's not a spice symbol.

Thank you for you comprehensive answer! I changed MOSFET to one from Spice Library and simulation ran correctly. Wish you a "bugless" undo of ngspice tricks :)

Thanks! Now, if we can just make finding models in the library easier...