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How to calculate the parasitic capacitance from Spectre simulation results

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haoyun

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Hi all,
anyone can tell me how can man calculate the parasitic capacitanc, ( for example, Cgs, Cdb,Cgd,Csb.....) from simlation's results by Spectre.


Regards.

Haoyun
 

how calculate Cgs?

You don't really have to calculate it. Just go to the ADE and click on Results->print->DC Operating point and select the transistor

That's the easiest way to see the results. There are obviously more
 

Re: how calculate Cgs?

make dc analysis
then open calculator and click op button
sellect component (for example mosfet)
choose parameter from the list box that will be opened
 

Re: how calculate Cgs?

But there are Cgs and Csg, which is correct?
(for example Cgs=-16.11f and Csg=-15.65f)


Thanks your reply!
 

how calculate Cgs?

Check one of the transistor model books how the capacitances are modelled, then you will find:

Csg=-dQs/dVg
Cgs=-dQg/dVs

So, that is not really that Cgs what you think I guess...

so the first letter is the charge, the second is the voltage... This rule is applicable for all the other transistor DC operating point capacitance parameters in the Meyer model

I usually use the Cgg (dQg/dVg), and in dependent on the region of the transistor estimate Cgd and Cgs, that is not accurate but ....
 
Re: how calculate Cgs?

haoyun said:
But there are Cgs and Csg, which is correct?
(for example Cgs=-16.11f and Csg=-15.65f)


Thanks your reply!
Click to expand...


The real answer is that Cgs and Csg does not represent physical values (i.e thoose from the books). They are part of the simulation model. For example, values of the Cgs are different for spice and spectre simulator, but simulation results should be the same.
 

Re: how calculate Cgs?

Thanks your reply!

Best Regards.


Haoyun
 

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