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Output of Kv when my rail-rail is 15v

write2rammy

 Hallo all,

         I have implemented a thermistor and ofet using verilog-A and designed a simple temperature sensor. I give a Vdd of -15V but the sensor output is in Kilo volts. I have attached the necessary files. Could somebody tell me what is wrong with it? Is it the simulator or the model?

temp_sensor.zip

  • It's extremely likely it's due to the models. Quite often this kind of problem occurs when you have a model with a quadratic equation (or higher power) driven by an ideal source (say) and no limiting in the model. The model may only be valid within a certain region, but the quadratic equation has multiple roots, and because there's no limiting, the simulator is quite at liberty to find a solution which is non-physical (because there was nothing in the model to ensure that the results didn't reach the non-physical solution).

    I've seen this problem several times with non-linear resistor models - the simulator can solve for a perfectly valid solution (according to the equations it is given).

    I see from a very quick scan of your model that there are some quadratic equations in there.

    There's no netlist or simulation options, so very hard to know how you've simulated it.

    It's extremely unusual (you just don't see it) for spectre to suffer from false convergence - unless the model has a non-physical solution.

    If you need more information, I'd suggest providing a complete testcase showing the problem, ideally to customer support at http://support.cadence.com .

    Best Regards,

    Andrew.

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