BSIM4 import into AWR

Hi Chris,

It's possible to import spectre models into MWO by importing them as a spectre netlist.   When you do so, you need to ensure that you are importing all of the model as most model files you find in a PDK will be referencing other files to get things like corner and/or mismatch info and all necessary parameters need to be clearly defined for it to simulate.

To actually use the model in an MWO schematic you need to call it from a simple netlist of the format:

simulator lang=spectre

inline subckt devicename (D G S B)
    parameters w=5u l=0.25u
    M0 D G S B mymodelname w=w l=l
ends devicename

model mymodelname bsim4
+type    = n
+version = 4.4
+lmin    = 2.5e-7
...
...
...
+noic    = 1.4e-10

This will give you a device you can place on a schematic which is scalable for w & l.    The spectre netlist parser in MWO is fairly basic so if there are special characters in the parameter names you may need to do some manual cleanup before it'll import and simulate correctly.

Graeme

Hi Graeme,

Many thanks for the reply, much appreciated. 

I have used this template and imported the BSIM variables manually and converted all the complex equations to values and it is working now (at least the DC part). Yet to test the AC and nonlinear HB but at least the sim is running now without errors.

Only thing is that I am getting a couple of warnings: "Source conductance reset to 1.0E3mho. (BSIM4!_S1_nfet33)", and "Drain conductance …." (where nfet33 is my devicename)

Doesn't make much sense as when I change the w, the Drain current seems to scale correctly. Just wondering if you know what these warnings refer to?

Best Regards,

Chris.

Hi Chris,

I wouldn't worry about that warning, these relate to DC operating points calculated by APLAC representing the internal terminal resistance.  If this isn't being calculated from the given parameter set then forcing a small resistance aids convergence.

Graeme

Many thanks again Graeme. Yes this works without warnings now. I have created three internal pins 11, 21, 31 before the BSIM model and placed an inductor/resistor circuit in these.

Below is the code (for anyone else trying this).

Best Regards,
Chris.

inline subckt mynfet ( d g s b )
parameters w=1.0e-6 l=0.25e-6

lg  (g 20 ) inductor l=1.000e-15
rg  (20 21 ) resistor r=1e-6

ldrain ( d 13 ) inductor l=1.000e-15
rdrain ( 13 11 )  resistor r=1e-6

lsource ( s 33 ) inductor l=1.000e-15
rsource ( 33 31 )  resistor r=1e-6

mynfet ( 11 21 31 b ) mybsim l=l w=w

model mybsim bsim3v3 version=3.2 type=n  capmod=2.0000e+00 \
 mobmod=1.0000e+00  nqsmod=0.0000e+00  noimod=3 \
    nch=2.3100e+17 vth0=4.6550e-01 \
....
....(REST OF BSIM DATA)
...

ends mynfet