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    Read inverter Capacitance/32nm BSIM4 MOSFET model in HSPICE

    Hi,

    I'm using the 32nm BSIM4 silicon MOSFET model to make an inverter in this technology. I'm trying to read the input capacitance of this inverter, but if I run a transient analysis and print the capacitance at the input node of the inverter using cap(input node), the values that I get are very different from the publications that I have been reading.

    My question is, when I print the nodal capacitance at the input of the inverter, does HSPICE include all the parasitics that the BSIM4 model takes into account, the intrinsic gate capacitances of the nmos and pmos devices and the Miller effect? If not, is there a better way to read all these capacitances correctly than using cap(input node).

    I have gone through the BSIM4 manual which explains all the capacitance models that has been used, but I couldn't find the answer to this question.

    Thanks in advance.

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    Re: Read inverter Capacitance/32nm BSIM4 MOSFET model in HSP

    Quote Originally Posted by aceyhan
    ... does HSPICE include all the parasitics that the BSIM4 model takes into account, the intrinsic gate capacitances of the nmos and pmos devices and the Miller effect?
    Actually, all *SPICE simulators are just calculator programs which solve the equations presented in the BSIM suite with the values given from the models. So you may be sure that all capacitive effects will be considered which are contained therein, and exactly so as they play their roles in the given schematic, i.e. e.g. the Miller effect contribution will be calculated according to the stage gain.

    Quote Originally Posted by aceyhan
    ... is there a better way to read all these capacitances correctly than using cap(input node).
    If you don't want to add all caps of a certain node manually, then just inject a unit current into this very node (against GND), and run an ac or xf analysis over a frequency range of your interest. The frequency dependent voltage generated at this node will directly show you its impedance, from which you can calculate the total node capacitance.



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  3. #3
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    Read inverter Capacitance/32nm BSIM4 MOSFET model in HSPICE

    Thank you...

    I have another question about HSPICE. Is it possible to print the parasitic capacitances such as the gate to drain capacitance, drain to bulk capacitance etc. Surely, SPICE takes these into account and calculates each of these at the background, but is it possible to print the values just like we print the node capacitances in the netlist?

    Thanks



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    Re: Read inverter Capacitance/32nm BSIM4 MOSFET model in HSPICE

    Quote Originally Posted by aceyhan View Post
    Thank you...

    I have another question about HSPICE. Is it possible to print the parasitic capacitances such as the gate to drain capacitance, drain to bulk capacitance etc. Surely, SPICE takes these into account and calculates each of these at the background, but is it possible to print the values just like we print the node capacitances in the netlist?

    Thanks
    Yes,
    Use the command
    .options captab post
    .print dc cap(node where you want to measure)



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