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So there are two formulas of the common mode rejection ratio (CMRR). I will mention the one that has the open loop gain. It is because someone asked me if the open loop gain and closed loop gain are enough to be able to compute for a CMRR or if there needs to be more given values.

CMRR = AOL / ACM

  • CMRR - Common Mode Rejection Ratio
  • AOL - Open Loop Gain
  • ACM - Common Mode Gain

But what if ACL was given instead of ACM? Are they the same? I think they aren't. I think there is a relationship between open loop gain, closed loop gain and feedback that can be computed from this thread. How do the open loop voltage gain and closed loop voltage gain differ? But I don't know how that relates to the common mode gain for me to eventually get the CMRR. Is there a way to do so?

I guess for someone kind of lazy but knowledgeable, a simple answer such as "No, there has to be an additional given to solve for the CMRR" would suffice because the question might sound really stupid. That would probably be enough. But I would appreciate more explanations. Thank you.

AndroidV11
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    So there are two formulas... No, stop! The world isn't about formulas. The world is about systems and interaction and here: circuits. So show what circuit (or system) you're talking about. I can design a circuit that has common mode rejection, so the CMRR can be determined, but my circuit does this without feedback. So there is not "open loop" so your formulas do not apply. Formulas can be used to describe how systems / circuits behave. So without showing the system / circuit formulas are utterly useless. – Bimpelrekkie Oct 16 '20 at 09:09
  • You've asked 11 question now and you haven't formally closed down any by accepting the most relevant answer. It's not like every question has all bad answers so, maybe you didn't know you were required to do this. Give and take. Think about it. – Andy aka Oct 16 '20 at 09:37
  • Yes I did not know this. Now I accepted most of the best answers in my questions. By the way, I am talking about the really common operational amplifier circuits. Let's say a non-inverting amplifier. – AndroidV11 Oct 16 '20 at 20:58

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