| Author |
Message |
haoyun
Joined: 10 Oct 2005
Posts: 80
Helped: 13
|
 01 Oct 2008 8:34 how calculate Cgs? |
|
|
|
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
|
|
| Back to top |
|
 |
PaloAlto
Joined: 08 Oct 2007
Posts: 131
Helped: 15
Location: Sevilla, Spain
|
| 01 Oct 2008 9:21 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
|
|
| Back to top |
|
|
pixel
Joined: 16 Sep 2004
Posts: 569
Helped: 59
|
| 01 Oct 2008 14:58 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
|
|
| Back to top |
|
|
haoyun
Joined: 10 Oct 2005
Posts: 80
Helped: 13
|
| 01 Oct 2008 16:59 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!
|
|
| Back to top |
|
|
drabos
Joined: 03 Jan 2006
Posts: 432
Helped: 27
|
| 01 Oct 2008 20:15 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 ....
|
|
| Back to top |
|
|
pixel
Joined: 16 Sep 2004
Posts: 569
Helped: 59
|
| 02 Oct 2008 20:24 Re: how calculate Cgs? |
|
|
|
| haoyun wrote: |
But there are Cgs and Csg, which is correct?
(for example Cgs=-16.11f and Csg=-15.65f)
Thanks your reply! |
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.
|
|
| Back to top |
|
|
haoyun
Joined: 10 Oct 2005
Posts: 80
Helped: 13
|
| 03 Oct 2008 17:58 Re: how calculate Cgs? |
|
|
|
Thanks your reply!
Best Regards.
Haoyun
|
|
| Back to top |
|
|
