Using CapTab for capacitance calculation

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jayeshbagada

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hey friends

using CapTab
can anybody tell me why at all we get capacitances in DC analysis(Capacitance being open in DC).

and since i am going to use my transistor in SRAM. in which analysis(AC,DC,Transient) should i use Captab to get parasitic capacitances.


Thank you
Jayesh
 

Hi,

You should use the captab option combined with the dc analysis since the various node capacitances of your circuit are strongly depended on the dc operating point of the various devices you use.
 

If u are using spectre as simualtor, then u can find capacitance at DC and transisent.

Capacitor is open to DC -- capacitor cannot pass a DC signal however u can still charge a capacitor using a DC signal. capacitance is ability to hold charge.

CapTab in Transient in Spectre . choose tran analysis -> options -> click on misc tab and click on captab checkbox , then click on output tab and enter time u want the cap to be calculated in infotimes entry.
if u dont enter infotime the capacitance will be computed for the last tran time step. u can enter 1 or more time point in infotimes seperated by a "space". u can view the result using capacitance table under result->print->capacitance table
 

Thanks for the information,

I'm using this but I'm not able to translate the table, like for example for one transistor there are 7 nodes! And those are like this:
T1:int_SI
T1:int_GP
T1:int_DI
T1:int_BS
T1:int_BP
T1:int_BI
T1:int_BD

Does anybody know what these are?

Thanks.
 

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