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Regarding problems with pmos characterisation

Pawanshekar

Hello, My name is Pawan Somashekar. I work as an Intern in Analog Design. I want to design an op-amp using Gm over Id method. In this case initially we have to characterise NMOS and PMOS transistors for various performance metrics like transconductance efficiency, transit frequency and so on. I  successfully characterised these for an NMOS transistors but when I'm simulating a PMOS transistor I'm encountering an error as show in the attached picture. I have tried several other ways to characterise the PMOS but I was unsuccessful. Kindly please help me. Thanks in Advance.

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  • Andrew Beckett

    Without knowledge of that particular design kit (PDK) it's hard to know. The warning above the error message is revealing though, because it suggests that the dimensions you've given for the device are out of the expected range. I wonder if it's expecting the dimensions to be given in microns rather than metres? What are the default values shown for an instance of that transistor (when you place a new instance)? There may be a scale factor applied during netlisting or in the models.

    You would be best to ask the foundry (the provider of this PDK) because it's hard to guess what might be wrong (other than my guess above).

    Regards,

    Andrew.

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  • Andrew Beckett

    Without knowledge of that particular design kit (PDK) it's hard to know. The warning above the error message is revealing though, because it suggests that the dimensions you've given for the device are out of the expected range. I wonder if it's expecting the dimensions to be given in microns rather than metres? What are the default values shown for an instance of that transistor (when you place a new instance)? There may be a scale factor applied during netlisting or in the models.

    You would be best to ask the foundry (the provider of this PDK) because it's hard to guess what might be wrong (other than my guess above).

    Regards,

    Andrew.

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