What variables are they?

[thanhFF]

Hi all,

I am doing a parametric analysis on an inverter by using Spectre. The PDK used is GPDK045 from Cadence.
The circuit and setting are shown in tha t .

My question is beside W(The Width of PMOS), what are other 3 variables(fw, P, iP) come from? What are they? When I point at them and select Find, it said not in the schematic, just only W can be found.

I tried the same method for inverter made from NCSU AMI 0.6. Everything worked fine, so wondering why MOSs from GPDK045 have some unknown variables?
Anyone has anything ideas?

Thanks

These are 4 pics included
1. Schematic
2. Test bench
3. Parametric Analysis Setup
4. 4 Variables on the left, 3 unknown

Also have log file after run Spectre.

 

[digi]

what is the value of Vin in your second picture?? i think you need to assign a dc value since you are using vdc as input(alternatively you could use a vpulse as the input).
there are no such variables like fw,P,iP as can be seen from the screenshots. i have used gpdk180 and have not faced any such error. you can do one thing-select each component, right click on properties and check whether any such variable is being shown or not.

 

[thanhFF]

@digi The purpose of this simulation is to determine the size of PMOS so the on-resistance of PMOS and NMOS are the same when transistors on.
With the Vin I swept it from 0-1V; Vdc = 1V as well. So if the simulation can run, I would see something similar to this picture(Vdd here is 5V).



From there I will pick the optimal PMOS size.
Sorry for the blurry snapshot. I reupload it, please see variables in the red rectangle.



I did check the properties of PMOS, besides width w, I found no other variables, but when I ran the simulation, it just said "found new variables", that really confused me .

Have you ever tried some sort of similar simulation on gpdk180? No problem at all?