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LM324: gain margin/phase margin circuit build

Part Number: LM324
Other Parts Discussed in Thread: TINA-TI



can you help me。LM324PWR application circuit is shown in the figure above。

we want to simulation its gain margin/phase margin。

how to build simulation circuit。

please give me some help。

  • Hello, 

    We have videos series under TI Precision labs to help guide on stability simulation. The videos specifically show how to set up and post-process in TINA-TI.

    Please see the following videos:

    Please let me know if you have further questions.
    Thank you!


  • dear Ashley

    thank you for your reply。

    I have watched the video,but i have a question。

    Why disconnect the loop? The actual loop is closed loop, is it not more suitable to simulate the actual loop directly。

  • Hello user6483709,

    The reason we run open loop analysis is due to the mathematical definition of what causes instability. 

    Acl = Closed loop Gain

    B = Feedback factor

    Aol = open loop gain

    Aol*B = loop gain.

    The relationship between the closed loop gain and the open loop gain is such:

    Acl = Aol/(1+Aol*B) 

    So going back to what causes instability, if Aol*B = -1 then  Acl would be undefined as the denominator would be zero. So when we run stability analysis we are looking for when Aol*B = -1. The two parameters left are Aol and B, hence why we want to open the loop to see Aol. 

    This is covered in more detail in the Stability - 2 video

    Hope this helps! 

    Best Regards,

    Robert Clifton