How to plot Id-Vg at different channel length by cadence spectre ?

You would need to setup up paramAnalysis() to tell it to do a parametric sweep of the length M0 (put a design variable in the Length field of the instance of M0, and then sweep that with paramAnalysis).

Then rather than using run(), you use paramRun(), and the plot would remain the same (probably better to use i("/M0/D") rather than getData - the graph will be the same but the legend on the graph is a bit more meaningful

Regards,

Andrew

Hi Andrew,

But how can I define a design virable in the Length field of the instance of M0?

I noticed that I can select the "Component Parameter" l (represent gate length) of M0 when I set "sweep virable" in choosing analysis. And the Vg curve of l sweeping is available by the script:

analysis('dc ?saveOppoint t ?dev "/M0" ?param "l" ?start "0.2" ?stop "0.6" ?step "0.05" )

desVar( "Vd" 0.1 )
desVar( "Vg" 2 )
desVar( "Vs" 0 )
saveOption( 'currents "all" )
temp( 27 )
run()
selectResult( 'dc )
plot(getData("/M0/D") )

Then I modify my script to  make parametric analysis:

analysis('dc ?saveOppoint t ?param "Vg" ?start "0" ?stop "2" ?lin "1000" )
desVar( "Vd" 0.1 )
desVar( "Vg" 3 )
desVar( "Vs" 0 )
desVar( "/M0/l" 0.18 )
saveOption( 'currents "all" )
temp( 27 )
paramAnalysis("/M0/l" ?values '(0.18 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6))

But Error raised:

bad name "/M0/l", not added

The variable "/M0/l" is not defined in the current design.

What Can I do now? 

You cannot perform a paramAnalysis on component parameters - only on design variables. That's why I suggested using a design variable. You can do dc analyses etc on component parameters - that's different.

So you need to edit your schematic, select the instance M0, and do Edit Properties. Set the value of "l" to say "LENGTH" and then you can have a desVar("LENGTH") and can do a paramAnalysis where you vary the variable "LENGTH".

Pretty straightforward.

ADE XL (and OCEAN XL) allow you to sweep arbitrary component parameters, so that would be another possibility.

Regards,

Andrew.

Hi Andrew,

Thank you very much. I followed your direction and get what I want.

Now I have a further question. 

I want to plot Vt vs Length @Vd=0.1V,  But I can't find a output "Vt", should I use some expression for such a character like "Vt" "Gm"?

richardyuan said:

Hi Andrew,

Thank you very much. I followed your direction and get what I want.

Now I have a further question. 

I want to plot Vt vs Length @Vd=0.1V,  But I can't find a output "Vt", should I use some expression for such a character like "Vt" "Gm"?

I've find the way to do this.  And I'll open a new thread to discuss the strange curve in detail.

Thanks.

Richard

Hi,

I am also facing the same problem but I cannot find a way to plot Vth in ADE XL.

If you've foun d a way it would be really helpful!

Thanks,

Amalia