• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 273 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM324: gain margin/phase margin circuit build

user6483709
Prodigy 60 points
Part Number: LM324
Other Parts Discussed in Thread: TINA-TI

Tool/software:

dear：

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。

  • 0
    TI__Genius 12960 points

    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: 

    https://ti.com/video/4080288067001

    https://ti.com/video/6341906518112

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

    Regards,
    Ashley

  • 0 in reply to Ashley Kang
    Prodigy 60 points

    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。

  • 0 in reply to user6483709
    TI__Mastermind 24730 points

    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