Hi,

I have couple questions regarding a BSIM3(V3.2) model file, especially the flow. I don't have deep knowledge about the modeling stuff, please bear with me.

We have this model from the foundry. There is a section, which I don't understand how it works. The section is given below between the # signs.

I understand that some where at the top the section "mos" is chosen and so we got to the point "subckt nch ( d g s b )". Since my transistors have the property "nch", we go into the "subckt nch ( d g s b )" as well.

What I don't understand is how do we get into the section "nch_model"? In this section the real transistor parameters are located.

What kind of special meaning does the word "mxckt" have? It seems like that makes it to go into the "nch_model" section.

In general, how is the flow in a model file controlled? Does the Spectre read the model file line by line, unless there is a specific command, which tells to the simulator to jump, like the "section" and "subckt" words.

For example, if we didn't have the word "mxckt", would we be stilling going into the "nch_model" section, even though my transistors don't have such property on it?

Thanks

################################################
.
.
.
section mos

subckt nch ( d g s b )
parameters w=10e-6 l=10e-6 as=0 ad=0 ps=0 pd=0 count=1
+ ...
+.. (Bunch of parameters in this portion)

mxckt ( d g s b ) nch_model w=w l=l as=as ad=ad ps=ps pd=pd

model nch_model bsim3v3  {
    0: type=n
.
.
.
################################################

Geoffrey_Coram wrote on Sep 16^th, 2010, 5:09am:

Hi Geoffrey,

Thanks for your reply. I see what you mean.

The line "mxckt ( d g s b ) nch_model w=w l=l as=as ad=ad ps=ps pd=pd" represents a single transistor, in which the parameters "w=w l=l as=as ad=ad ps=ps pd=pd" come from the subckt call one above and the transistor uses the model "nch_model"