Ok Fair enough, that was a silly question. i will work out those curves myself and try to understand whats behind each one of them.
I must admit that I got so excited, I was trying to get a few weeks ahead of schedule with lectures and try to reproduce&simulate a JFET 2N3819.
what did i do:
I reproduced the circuit (I believe now I understand the symbols-spice issue) however,
I used a Q_NJFET_DGS as that exact model doesn’t seem to be on KiCAD library,
changed the value field,
created a spice library for the jfet (called jfet_2n3819.lib) and added it through the component properties (as I did for the BJT)
run a simulation with the following:
DC Transfe,
sweep VDD
0 10 1m steps
Run: it returns that component/symbol error again
Thank you for the reply.
Interestingly, even before reading it, i thought: why don’t you use another JFET (as I looked on the web and I couldn’t find a spice model for that particular transistor)?
So, I tried 3 more transistor JFET from the KiCAD library. It turns out that it was really hard to find spice models for these too in fact, i couldn’t find a spice model for any of them.
Is it like this for most other components too?
Am i wrong to conclude that learning to write your own spice model using info from manufacturer’s data-sheet is the only way forward here?
I am taken aback of the fact that this is an actual assignment due in a few weeks and I am pretty sure that the tutor will be able to offer students with a spice model taken from the LTSpice database. I guess I could wait and use that one
So, it’s not for “most” of them, but for all of them. Out of the box, just the basic parts such as voltage sources, resistors, capacitors and such are supported.
You can of course write your own spice models, but plenty of others have already done that, or have made collections of “stuff” found on the 'net.
This may be a good place to start:
But just as a lot of KiCad symbols are generic and you have to add a footprint link yourself, you also have to add a link to the spice model to use for those schematic symbols.
Now, KiCAD does not have the symbol, so i went through this line of thinking:
use any other JFET change its name and value, add the spice model from a file.lib that i create and voila’!
the first line of the error msg says: ‘No Compatibility Mode Selected’ - How/where from do i enable such compatibility mode? I looked everywhere i.e. in settings, symbol parameters,…
the msg is still pointing to the other (original) JFET that I used, bf246a; i thought that changing the symbol’s name/values wouldn’t do the trick but maybe changing the name of the file.lib as well as its content could work.
For the next issue, read the second line of your error message.
warning, can’t find model 'bf246a" from …
Apparently you’ve been able to change that yourself (in previous screenshots it was “q_njfet_dgs” or “2n3904”) and you should be able to change that again. Make some notes, etc.
We’re happy to help, but we’re also volunteers with a limited amount of time and expect some effort from your side.
As previously mentioned in my post, I’m not an NGspice expert. Regardless, the errors you’re seeing are clearly called out in the message…
To resolve the Errors, a couple of choices to consider:
Spice Models: Either download or, type the data into text file and Include in schematic.
The ‘data’ can come from spec sheets and/or from LTspice’s model info (thus, you can copy to your text file).
Models/etc need to correctly parrot the shematic’s Pin, Names, Labels…etc (meaning, if your transistor shows pins 123 but, the text file shows 456, well, you get errors. All references need to be accurate.
If you build the schematic in LTspice and it works but want to do the same circuit in Kicad, just make sure your data is accurate and if errors result, it will be easier to problem solve.
Images below show:
Simple examples in LTspice
Simple example in Kicad with an Include file for Diode
LTspice Data Panel for getting data to paste into a text file
I am trying to learn to stand up on my legs and what you think it being an attempt to run perhaps should be considered more as fast crawling.
I do not expect you to devote your free time to help me in fact, if i receive a reply today of next week it will still be highly appreciated.
Apparently you’ve been able to change that yourself (in previous screenshots it was “q_njfet_dgs” or “2n3904”) and you should be able to change that again. Make some notes, etc.
I did say that I tried 3 or 4 more transistor from KiCAD library and those you see are not name/values i changed, but just the transistors/symbols i used earlier. Changing the symbol again will give me the same error with a different
warning, can’t find model 'different_name_here" from …
Maybe, as i already realized, i was getting too excited and “crawling” too fast. So, i will take a break and focus on some theory.
If you take a schematic symbol from KiCad’s library it does not have any spice model attached. To add that, you hover over the schematic symbol on your schematic, press e to edit it’s properties, and then there is a button at the bottom of the properties window to adjust the spice stuff:
Hello everyone,
I am back with the usual newbie’s questions.
But, firstly, i better ask whether the forum moderators prefer to have a new thread for a different questions? or is it OK to file them up on this newbie’s topic?
I have run, successfully, a few DC sweep simulations this week and now I would like to add/learn about transient simulation, i.e. sinusoidal functions over time. More details to be added maybe in a new thread
Any inputs will be welcome and appreciated
