a question about Cgs and Csg in the circuit

[tanghua_0407]

when i do the simulation with the circuit ,the Cgs and Csg of the transistor are not equal ,why??

 

[xuel]

how do you get Csg?
In .lis file, there is oly Cgs information.

 

[cretu]

when i do the simulation with the circuit ,the Cgs and Csg of the transistor are not equal ,why??

A short question. are you sure thery are not equal? Or you have by any chance a different parasitic with respect to the substrate when you look from the gate or from the source? The reason I am asking these is that in any case they should be equal, but having different pqarasitics with respect to GND. U can see this in power technologies often

 

[gunturikishore]

The Bsim3v3 transistor model uses complex equations to solve the capacitances. Even the charge disribution in the channel can be different depending on the process and the options u choose. The capacitance is calculated as Cgs= ΔQg/ΔVs and Csg= ΔQs/ΔVg. Hence they vary in their magnitude. The more better approximation seems to measure at gate is Cgg=ΔQg/ΔCg, which is the summation of all. I am not quite sure and if somebody finds it wrong, please correct me.