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 Common Mode Input Range - Using Ocean 

Last post Tue, Nov 4 2008 8:49 AM by coco009. 0 replies.
Started by coco009 04 Nov 2008 08:49 AM. Topic has 0 replies and 1745 views
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  • Tue, Nov 4 2008 8:49 AM

    • coco009
    • Top 500 Contributor
    • Joined on Thu, Oct 2 2008
    • Posts 17
    • Points 250
    Common Mode Input Range - Using Ocean Reply

    This is relatively straight forward design question, so thanks to anyone who can help me.

     

    I am trying to calculate the CMIR for an op amp. At present, I have set up a testbench, where I use the op amp as a unity gain buffer and then I sweep the V+ input from 0V -> Vdd. Because I have a unity gain buffer, I am calculating the common mode input range as the range of V+ values, resulting in unity gain on the output, i.e where V+ = V-. 

     

    My question is ... is there a standard way of actually taking the measurement, where I can measure the CMIR (Vcmin, Vcmax)automatically, with an ocean command say. At the moment, I am plotting V+ and V- and estimating the CMIR values when V- deviates from a gain of 1. This is not really a very consistant method, so if anyone has any more "mainstream" methods of calculating these values, I would be very grateful.  

     

    Thanks in advance

     

    coco009

    • Post Points: 5
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Started by coco009 at 04 Nov 2008 08:49 AM. Topic has 0 replies.