how to calculate effective capacitance at node of circuit in ads 2013

[Ata-Va]

Hi every body
I wanna calculate effective capacitance at output node of my designed circuit. I am using ADS 2013 version of software.
Does ADS have any option to calculate it automatically or should i write an equation for it?
thx for you helps

 

[albbg]

If you want to measure the capacitance with respect to the frequency, place an AC generator between the node you want and ground (I suppose you want the capacitance referred to ground). The parameter save current has to be "yes". Then name the node, f.i. "out".
Do the simulation and in the result sheet place an equation to first calculate the inductance as Z=out/out.i (sorry I don't remember the exact synopsis and I've no access to ADS in this moment).
Then place a second equation to calculate the capacitance in F as C=-1/(6.28*imag(Z)*freq) or C=-1e12/(6.28*imag(Z)*freq) if you want pF.

 

[Ata-Va]

thx dear albbg for you reply
actually i don't wanna calculate the capacitance respect to frequency I have dc analysis and I wanna calculate the output capacitance, in Hspice there is a command for this purpose ".option captab".

 

[albbg]

I don't know Hspice, however I never used a similar command in ADS. It could be you find something under the operating point parameters.