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I'm modelling a feedback circuit in Ltspice, however, I want to work out the transfer function for it. See below for the circuit. enter image description here

Now I want the form of Vfb/VOA_o as: enter image description here

So, I've thought about breaking up the circuit into two constituents to solve for this, as follows.

enter image description here

Would you say that this is the best way to approach this? What is the transfer function, if this is not the correct approach?

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    \$\begingroup\$ It looks like a duplicate already answered here. You cannot separate the circuit into two separate paths as you do here. \$\endgroup\$ Nov 2, 2023 at 6:42
  • \$\begingroup\$ thanks for your response. I've had a read of your reply to the other thread with this, however, I am still unsure of how it answers my question. I'm looking for the transfer function in a certain format, so how would you approach stipulating it in such a fashion? \$\endgroup\$ Nov 2, 2023 at 6:45
  • \$\begingroup\$ I don't understand what you mean by "a certain format"? This is a 1st-order system and I presented the result in a clear and ordered form. What did I miss? \$\endgroup\$ Nov 2, 2023 at 6:58
  • \$\begingroup\$ what I mean is, I am trying to express it in the format shown above - a voltage divider multiplied with 1/(1+s/wp) \$\endgroup\$ Nov 2, 2023 at 7:00

1 Answer 1

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enter image description here

Find the transfer function for Vout/OA_ and then multiply it by a factor of 1/2 to get the transfer function for fb/OA_

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  • \$\begingroup\$ thanks for your response, just have a question, why do we multiply by 1/2 for the final form of fb/OA? \$\endgroup\$ Nov 2, 2023 at 7:21
  • \$\begingroup\$ alanwake29261 The 2 Rs form a resistive voltage divider. fb = Vout*R/(R+R) \$\endgroup\$
    – user350400
    Nov 2, 2023 at 7:43
  • \$\begingroup\$ oh alright, could you possibly outline it with the corresponding steps? \$\endgroup\$ Nov 2, 2023 at 7:59
  • \$\begingroup\$ @alanwake29261 Vout/OA_ = (Zc//2R)/(Rout+(Zc//2R)) then multiply your derived transfer function by 1/2. \$\endgroup\$
    – user350400
    Nov 2, 2023 at 8:37

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