MOSFET circuit gives the following error "unable to find definition of model"

[Geof D]

I am trying to simulate a simple MOSFET circuit and I keep getting this error "unable to find definition of model".

Any ideas would be appreciated,

Thanks,

Geof

[lacy]

Please post your ciruti file or a pictue of it. It would be hard to make a determination as to the cause of your problem without it.

[Geof D]

Here's the model info

M31 1 2 3 4 CMOSN L=1u W=1u
.MODEL CMOSN NMOS (LEVEL=3                 
+TOX=1.4E-8 NSUB=1E17 GAMMA=0.5483559         
+PHI=0.7 VTO=0.7640855 DELTA=3.0541177         
+UO=662.6984452 ETA=3.162045E-6 THETA=0.1013999         
+KP=1.259355E-4 VMAX=1.442228E5 KAPPA=0.3               
+RSH=7.513418E-3 NFS=1E12 TPG=1                 
+XJ=3E-7 LD=1E-13               
+CGDO=2.15E-10 CGSO=2.15E-10 CGBO=1E-10             
+CJ=4.258447E-4 PB=0.9140376 MJ=0.435903          
+CJSW=3.147465E-10 MJSW=0.1977689) 

and the circuit

Thanks in advance

Geof

[lacy]

That clears up a bunch of things here. The model information is not compatible with Multisim as is. The format for the Mosfets are the same for some of the other components in the fact that they need to start with the .SUBCKT line at the beginning of the model file and then at the bottom of the file there should be an .ENDS statement. They do not follow the standard .MODEL format like the diodes or transistors for some reason.

This of course is not the only problem with this model as I believe there are other issues about the model file that are causing problems (i.e parameters not being recognized or with incorrect syntax). I am no model expert (I know the basics about them) and I really could not tell you how to modify it to make it compatible.

Ni may be of assistance here as they are more knowledgeable about the model files than I. Or if another user has more experience with these files your expertise would be greatly appreciated here.

Sorry I couldn't be of much help in this situation.

[Geof D]

No problem.  Thanks for trying.

[OStep]

somewhere along the component creation process you made a mistake. You're component is faulty.

I have created a new for you. I wrapped the mosfet in subcircuit structure as this makes it easier to edit

[lacy]

Thanks Max for your assistance on this. I had everything right in my attempts execpt for the d g s b in the model declaration and the subckt statement. One question: Is it always necessary to have the MOSFETS in a Subckt format instead of just the Model format? The reason for the question is that I noticed that all the ones in the database are in this format while transistors, etc just use the Model format.

[Geof D]

Thanks guys for your responses.

Geof

[OStep]

Lacy -

If your entire simulation model consists of just the .model device then it is not mandatory to wrap it in a subcircuit structure. However, I prefer the subcircuit method as it forces you to write and gives you control over the mosfet instantiation statement (i.e m1 d g s s myMOS w=90u l=60u). Otherwise, without the subcircuit, Multisim automatically creates this statement and it will not be accessible through the 'edit model' button once the component is double clicked.

Thanks