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Is the device capacitance bias-dependent or independent?

Alex Liao
Hi, I would like to know if the device intrinsic capacitance like Cgs bias-dependent or independent. Giving say, bias 400mV or 500mV (common source circuit with Vgs = 400mV or 500mV) for 65nm technology, is the Cgs the same or different and why？

Thanks,
Alex
Parents

  • Hi Alex,

     >  I have got all 

    Excellent!

    > If this is not the case what is your interpretation on Capacitance from Spectre Simulation like Cgs. 

     My understand, Alex, is that the values of capacitance reported by Spectre are those of the BSIM model only and do not include any capacitances associated with the local interconnect or those due to routes to nearby components. The reason I believe this is the case is that when a netlist is created using the layout derived extracted view, all of the local interconnect capacitances and routing capacitances to neighboring devices are modeled by fixed capacitors all of which are external to the BSIM model capacitances cgs, cgd, etc... Therefore, Spectre must rely on just the BSIM model when computing the partial derivatives of charge to determine the operating point capacitances.

     

    What do you (or others) think Alex?

     

    Shawn 

Reply

  • Hi Alex,

     >  I have got all 

    Excellent!

    > If this is not the case what is your interpretation on Capacitance from Spectre Simulation like Cgs. 

     My understand, Alex, is that the values of capacitance reported by Spectre are those of the BSIM model only and do not include any capacitances associated with the local interconnect or those due to routes to nearby components. The reason I believe this is the case is that when a netlist is created using the layout derived extracted view, all of the local interconnect capacitances and routing capacitances to neighboring devices are modeled by fixed capacitors all of which are external to the BSIM model capacitances cgs, cgd, etc... Therefore, Spectre must rely on just the BSIM model when computing the partial derivatives of charge to determine the operating point capacitances.

     

    What do you (or others) think Alex?

     

    Shawn 

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