How to sweep the ndet width

Hi,

I want to sweep the transistor width and plot the gain of the op-amp
with the frequency. My op-amp is differential. But the ac analysis only
allows sweep of one component parameter in ONE component. I want to sweep
the widths for the differential nfet pair. Can anybody teach me how to do
it?

Another difficulty I have is: since I sweep the differential pair
widths and frequency at the same time, how can I configure it in the ac
analysis? I want to draw a group of gain plots with different widths for
the transistor pair.


Kuan

 

You are looking for the Parametric analysis, which can be found under the tools
menu in the simulation environment
Setup your AC frequency sweep like you are used to. Define your designvariables
(w, l) and then setup the parameter analysis. It will run an AC for every
combination of parameters you setup.

Have a look into the documentation for further informations.

Marc

 

an advice: beware of CDF callbacks. for plotting the gain, it wouldn't
change, but if you were plotting AC response then make sure the MOS
as,ad,ps,pd are not computed by a CDF callback - it happens - because
callbacks are only called when changing from the UI.

alternatively use a MDL control file.

stéphane

 

Hi,

What is MDL control file?

Kuan

 

MDL - measurement description language. a somewhat new feature in spectre (IC5032 i believe).

look into mdlref.pdf ("Spectre MDL User Guide and Reference")

i'm lazy, the following example is from the manual, it demonstrates nesting loops.


alias measurement findmax {
run tran(stop=1u) export real maxout=max(out)
}

foreach vdd_val from swp(start=5, stop=7, step=0.5) {
foreach temp from swp(start=25, stop=75, step=25) {
run findmax
}
}

stephane