[Moved]: using measure in HSpice

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Renato_PERU_1979

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People, please, I'm new in the use of HSPICE, so I need some helps. I tried to simulate somethings with a mosfet. and I tried to find the maximun point in the deriv('sqrt(id(mn1))') and the Vgs for that point, and the sqrt(id(mn1)) for the same Vgs point. I know that I can do that using par functions and plotting in cosmo scope, but I want to use the Measure command. I did something like this to find the maximun point in the deriv('sqrt(id(mn1))') and the Vgs for that point:

Code: 
.measure dc deriv_sqrt_id_max max deriv'(sqrt(id(mn1)))'

The hspice gave me the good answer : deriv_sqrt_id_max= 5.7847E-03 at= 1.1300E+00

But the problem is when a tried to use the same command .measure to find the sqrt(id(mn1)) in that point. I tried something like this:

Code: 
.measure dc deriv_sqrt_id_max max deriv'(sqrt(id(mn1)))'
.measure dc sqrt_id find par('sqrt(id(mn1))') when par='max(deriv(sqrt(id(mn1))))'

I know that I wrong in the last code, but I tried to explain what I want, something like "to nested" or "to link" the measure command. Is it possible?

Thanks!
 

Renato_PERU_1979 said:
Code: 
.measure dc deriv_sqrt_id_max max deriv'(sqrt(id(mn1)))' 
.measure dc sqrt_id find par('sqrt(id(mn1))') when par='max(deriv(sqrt(id(mn1))))'
Click to expand...

In your 1st .measure statement (which worked), you used 'quote signs' for the deriv expression term. Try this in your 2nd statement, too:
Code: 
 .measure dc sqrt_id find par('sqrt(id(mn1))') when par='max(deriv '(sqrt(id(mn1)))')'

If this doesn't work either, try a comparison within the when expression:
Code: 
 .measure dc sqrt_id find par('sqrt(id(mn1))') when par('sqrt(id(mn1))') = par(max(deriv '(sqrt(id(mn1)))'))
 


Hi erikl ! thanks a lot for your help! but the code didn't work yet. Now I'll tried to do a better explanation about the simulation that I want. The circuit is like this:

Code: 
Vdd 1 0 gs
mn1 1 1 0 0 n L=2u W=2u

.dc gs 0 2 1m 
.option probe 
.options dcon=1 
.probe dc id(mn1) 
.probe dc sqrt_id=par('sqrt(id(mn1))')
.probe dc deriv_sqrt_id=deriv'(sqrt(id(mn1)))' 
.end

And in cosmoscope I see two graphs:

plot 1: deriv_sqrt_id vs. vgs. Here I take the maximun point of the derivative of the square root of id(mn1) with the corresponding value of vgs, say "vgs_o".
plot 2: sqrt_id vs vgs. Here I take the value of the square root of id(mn1) at "vgs_o". This voltage "vgs_o" is already known from the plot 1.

So, if I use the .measured statement to know the same results that in plot 1, I write:

Code: 
.measure dc deriv_sqrt_id_max max deriv'(sqrt(id(mn1)))'

and the hspice answer: deriv_sqrt_id_max= 5.7847E-03 at= 1.1300E+00. That's ok!

But I don't know how can I get -using the .measure command- the square root of id(mn1) at the "v_gso " value, obtained in the former .measure, where it was gotten 1.1300E+00. Is there any way to link the "v_gso" that gets HSPICE to evaluate in sqrt_id=par('sqrt(id(mn1))') function to get the proper sqrt(id(mn1)) in that "v_gso" value?

thanks a lot!!!
 
Last edited:


It's possible, but I don't know exactly how. Here a few snippets from the HSPICE® User Guide: Simulation and Analysis B-2008.09 which possibly might help you:
View attachment Running_HSPICE_Interactively.pdf

Perhaps you can use the parameter deriv_sqrt_id_max directly. Try a few of these variations, either with at or when:
Code: 
.measure dc sqrt_id find param=”sqrt(id(mn1)” at= deriv_sqrt_id_max
.measure dc sqrt_id find param=”sqrt(id(mn1)” at= par(deriv_sqrt_id_max)
.measure dc sqrt_id find param=”sqrt(id(mn1)” at= par=’deriv_sqrt_id_max’
 

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