ask a question about Cds of MOSFET

[patriot]

in SMIC's mos model,it gives a value of Cds= -1.392E-20*(N*W/L)*(N*W/L)+5.792E-17*(N*W/L)+1.938E-14," Cds and Rds model the high frequency characteristics between drain and source." what is the capcitance? in RAZAVI's book,there's no mention about it

meanwhile,if I use PPOLY/NWELL and connect the Drain,source,Bulk together,by controlling the votage of Vgs,how to compute the Capitance of Vgb

thanks for any suggestion

 

[patriot]

can anyone help me ?

 

[noiseless]

you question is not clear. what capacitor you want to calculate? In you attached file, what do you want to say. If you connect G,B, and S, what you measured is gate capacitor (at some Vgb, it in series of the depletion cap).

 

[patriot]

first,i wanna know what deoes Cds refer to ?
the second : if i connect B S D together as the attachment described,what capacitance does the varactor include? if it means the oxide cap in series with
depletion cap?
many thanks!