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 fully differential opamp .. how to calculate cmrr ?? 

Last post Tue, Feb 18 2014 11:38 AM by Andrew Beckett. 2 replies.
Started by rakesh reddy 17 Feb 2014 10:00 PM. Topic has 2 replies and 1919 views
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  • Mon, Feb 17 2014 10:00 PM

    • rakesh reddy
    • Not Ranked
    • Joined on Thu, Sep 5 2013
    • hyderabad, Andhra Pradesh
    • Posts 6
    • Points 105
    fully differential opamp .. how to calculate cmrr ?? Reply

    I made this schematic and I simulated this I am getting gain ~40dB and UGB 20Mhz,

    I want to do stability analysis for this fully differential ckt ,

    And I want to find out

    --- CMRR

    --- PSRR

    ---Loop gain (from stability analysis  )

    How I should use cmdprobe to do stb analysis , please help me ,, 

    adrew sir ,, can you please provide me a link with an example how to procede ..


    • Post Points: 5
  • Mon, Feb 17 2014 10:12 PM

    • rakesh reddy
    • Not Ranked
    • Joined on Thu, Sep 5 2013
    • hyderabad, Andhra Pradesh
    • Posts 6
    • Points 105
    Re: fully differential opamp .. how to calculate cmrr ?? Reply
    here is the cmfg and biasing circuitary ..
    • Post Points: 20
  • Tue, Feb 18 2014 11:38 AM

    Re: fully differential opamp .. how to calculate cmrr ?? Reply

    I already answered some of this in your previous post (it wasn't clear whether you'd read the reply, since you're repeating some of the same questions).

    Some info can be found in solution 11179406 on Cadence Online Support. Essentially you're inserting the cmdmprobe (or diffstbprobe if using a more recent version) in the feedback loop(s) of your differential circuit, and then setting the CMDM parameter to either +1 or -1. When specifying the probe on the stb analysis form, point at the cmdmprobe instance and it will set things up appropriately. If using diffstbprobe, it will offer you the choice on the analysis form as to whether you want differential or common mode stability.

    Regards,

    Andrew.

    • Post Points: 5
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Started by rakesh reddy at 17 Feb 2014 10:00 PM. Topic has 2 replies.