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Query regarding interpretation of Drain/Source Periphery and Drain/Source Diffusion Area of Mosfet in Spectre

PritiG

Hi,

I made a circuit with a couple of MOSfets..without worrying about the as , ad , ps and pd and simulated on Tanner and got the desired results. When i made the same circuit on cadence schematic editor , in the properties of the mosfets, the as, ad, ps and pd got set according to the Widths of the Mosfets and the other important rules like contact size, poly contact spacing and min active contact enclosure from the design rules file. But when i simulated the circuit on spectre, the response of the circuit changed significantly.When i removed the as, ad, ps and pd then in Spectre also i got the expected response. When i added the same as, ad, ps and pd generated in cadence schematic editor back into tanner, i still got the expected response. 

 This makes me feel that Cadence spectre is handling these parameters somewhat differently from other simulators. I want that my circuit should work exactly the same way on both the simulators since im using the exact same devices and parameters. Could someone please throw some light on how spectre handles these parameters so i could make the necessary changes to my circuit to get the correct response.

Thank you and Regards,

Priti 

  • Priti,

    There's nothing particularly unusual about how these are handled in spectre compared with other simulators. There is some support for auto-calculating them within the simulator (for some models) depending on other model parameters set.

    If your design kit is auto-calculating these when  you create the instance, and you have doubts about the accuracy, you should contact the provider of the design kit. 

    This is a very basic capability and spectre should do the right thing here...

    Of course, feel free to contact customer support and then we can look at the specifics of your simulation and simulation results to make sure that everything makes sense.

    Andrew

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