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  • TI Thinks Resolved

Tim Green's series on Op Amp Stability

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Replies: 8

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Several TI documents reference Tim Green's 15-part series on Operational Amplifier Stability.  I have done extensive web searches, and have managed to find a few parts piecemeal.  Is the entire series available anywhere?  Please advise.  Thanks.

  • The basis of the article series can be found here:

    http://e2e.ti.com/support/amplifiers/precision_amplifiers/w/design_notes/2645.solving-op-amp-stability-issues.aspx

    En-Genius where the articles were originally published is no longer a Web Magazine.  I attach the 11 parts completed in the zip file attached to this post.

    Let me know if any questions.  Thanks for your interest.  

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

    Tim Green, SMTS
    Precision Amplifiers Applications Manager
    
    		
    TG Stability_All pdf.zip
  • In reply to Tim Green1:

    When will be graced with parts 12 - 15?

    -Ken

  • In reply to Ken Dillinger:

    Parts 12-15 will be included in the Op Amp Stability book in development.  Hopefully, completed over the next two years.  In the mean time we are here to support any op amp stability problems you may encounter....

    Thanks for your interest in the technical writings.

    Tim Green, SMTS
    Precision Amplifiers Applications Manager
    
    		
  • In reply to Tim Green1:

    When will the operational amplifier stability book be launched?

    This is a very good material of understanding op and stability.

    Few material deals with this area.

    Hope it will come in as soon as possible!

  • In reply to Charles Cheng:

    Book is still a work in progress.  For now the link below has some good material put together by myself and my stability colleague, Collin Wells, that is a subset of the book.  There are 4 parts to download.

    http://e2e.ti.com/support/amplifiers/precision_amplifiers/w/design_notes/2645.solving-op-amp-stability-issues.aspx

    Tim Green, SMTS
    Precision Amplifiers Applications Manager
    
    		
  • In reply to Tim Green1:

    Hi Tim,

       any ideas about how to calculate the stability of a differential operational amplifier?

  • In reply to Tony Wang:

    Tim,

    The op-amp doesn't know it's setup as differential  (difference) operational amplifier.

    None of the feedback goes to the non inverting input so it is not part of the stability analysis.

    Treat this amplifier setup the same as any other amp op circuit.

    Regards,
    Ronald Michallick
    Linear Applications

    TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).

     

  • In reply to Tim Green1:

    Hi!

    I am using the "Rate-Of-Closure" Stability criteria (Part 1 of 4) to analyze some different opamp networks at different temperatures. A weird behavior is occurring at low temperatures, at -40°C using OPA4188:

    In the plot above I am showing the loop gain graph for 25°C and -40°C. For the case of -40°C, since 1/beta is above Aol. My interpretation is: it means that there is no margin for Aol to fix 1/beta, so the circuit is unstable at -40°C, isn't it?

    We have tested a small lot in the lab (not isolated but connected to some others) and in some cases it has shown to be unstable (not all times, in every circuit of the lot), so I am looking forward to substantiate theoretically why we are observing such behavior.

    Thank you very much for your help.

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