MOS varactor structures

[tran]

Hi all,
I see people use transistor mos as varactor. But I don't know which capacitor of mos will vary, Cgs,Cgg,...? Can anyone explain for me which capacitor of mos will vary when we change bias voltage? how do it change its value, and the highest and lowest limit values.
Thank you very much for your help

 

[khouly]

when u do a mos varactor , so u connect the sorce and drain to be one terminal

so the cap is the total capacitance between source drain and gate

khouly

 

[hnejati]

This configuration as Khouly mentioned before known as MOSCAP. actually you can find bunch of relative texes on internet if you search for MOSCAP.