libraryltspicemodeltransistors
I'm trying to add the mmbt3904lt1g model to LTspice.
– I've copied its data from the MMBT3904LT1.LIB.txt in the standard.bjt library.
– I've added an NPN to my schematic then I've changed its value to mmbt3904lt1g
– through the Edit->spice directive I've pasted the path to this library
I thought it was all to use this device but no simulation is achieved.. I get only:
Can't find definition of model "MMBT3904LT1g"
where I'm doing wrong ?
From the LTSPice IV manual:
X. Subcircuit
Syntax: Xxxx n1 n2 n3... <subckt name>
[<parameter>=<expression>]
Subcircuits allow circuitry to be defined and stored in a
library for later retrieval by name. Below is an example of
defining and calling a voltage divider and invoking it in a
circuit.
* calling a subcircuit
*
* This is the circuit
X1 in out 0 divider top=9K bot=1K
V1 in 0 pulse(0 1 0 .5m .5m 0 1m)
* This is the subcircuit
.subckt divider A B C
R1 A B {top}
R2 B C {bot}
.ends divider
.tran 3m
.end
Notice that params: never appears in the LTSpice syntax for a subcircuit call.
I am guessing that including this token in your X card has confused LTSpice about how the subcircuit should be called.
This is defined as a subcircuit:
.SUBCKT PSMN2R0_30PL DRAIN GATE SOURCE
LTSpice needs this to have somewhat special treatment, so you will need to do the following:
CTRL+Right click on the device and you will get this window:
Now edit the Prefix and Value lines: The prefix for a subckt is 'X'. The model name is precisely as defined in the lib file.
Now click OK. You will need to add a spice directive on your schematic:
.include PSMN2R0_30PL.lib This assumes it is in the same directory as the simulation circuit.
LTSpice should now be happy with the part.
Here is what you should see on the schematic:
You can, of course, add it to the LTSpice model tree, but I find it easier to use this method.
Best Answer
If the model definition is a whole subcircuit (starts with .SUBCKT), you need to use the X prefix: Ctrl + Right click on the component, and set the prefix value to "X".
Also check that the Value is set according to the name of the SUBCKT.
Also check that you have an ".include" directive somewhere on your schematic, set with the correct path of the file. Alternatively, you can paste the entire component description within a spice directive block on your schematic, but it takes a lot of space.
I wouldn't recommend putting the definition within standard.bjt file, as you seem to have done. I think you can't put whole SUBCKT in there (I also seem to remember it requires restarting LTSpice).