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AC vs. PZ analysis

ASICnm

I have a complex opamp model built using ideal sources (no transistors models). I am interested in frequency response, so tried both AC and PZ analysis, to check the dominant pole (-3 dB), resulting as:

AC @ 59.24 MHz , and PZ @ 60.18 MHz. This is fairly close, then i compensate the model (miller compensation with nulling resistor) to stretch this pole from another nondominant pole. The resulting dominant pole reported by AC: 130 KHz, while PZ reports: 226 MHz (which is more convcingly a value for nondominant pole).

I want to know why are the values so different. Assuming there are no frequency dependent components used either (so freq eval may not help much) why does PZ misses the dominant pole altogether ?

Finally would jumping to IC 6.15 help for this particular issue ?  I am currently on IC 5.1.14, Spectre ver. 6.1.1.565

Regards,

 

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  • Andrew Beckett
    There is a "what's new" document (or documents) that you can access via "cdnshelp" (cdsdoc in older releases) which summarizes the major changes and innovations in each new release.

    Regards,

    Andrew
Reply
  • Andrew Beckett
    There is a "what's new" document (or documents) that you can access via "cdnshelp" (cdsdoc in older releases) which summarizes the major changes and innovations in each new release.

    Regards,

    Andrew
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