Transconductance and parasitic capacitance for NMOS

[chlee]

I am using Cadence Spectre to obtain model parameter and DC operating point for NMOS.

I am still a beginner in handling this software and I am confused of parameters that are showned.

For transconductance, is it enough to just using the parameter "gm"? There are gmbs and gmoverid which I am not familiar.

And for capacitance, I need Cgs and Cgd for my calculation purpose. There are cgdo, cgso, etc. The value of cgs and cgd are too small compared to cgdo and cgso in my case. Which one exactly is the capacitance that I should be looking at?

p.s.:Sorry for my bad english, I am trying my best.

 

[chlee]

Is there anybody can help me with this? I am quite confused of the terms given by Cadence, I need both value for my calculation.

Please help me...

 

[rshrivas]

Use calculator for find out the cap of the NMOS.

First do DC simulation, then open the calculator and select op.. then select the device (NMOS or PMOS).... The go back to the calculator and select op again.. This time it willl give u a drop down list.. It will have Cgs Cgd and other capaciatnce...

I alwayz use gm as trancondutance and ignore the rest.... hope that helps