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I was revising my notes and I stumble across this problem. In my notes, it says that a feedback circuit required some feedback elements to works. Let's take the integrator op amp as example: The feedback mechanism used is negative feedback, right? So inside this circuit, are the feedback elements R1 and C2? Or is there no need for any "feedback elements" for a feedback circuit to work?

schematic

simulate this circuit – Schematic created using CircuitLab

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3 Answers 3

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The feedback elements mean the elements in the feedback path. In the circuit you present the resistor and the capacitor of the integrator are the feedback elements.

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    \$\begingroup\$ I would argue that only the capacitor is a feedback element. \$\endgroup\$ Jun 3, 2020 at 16:46
  • \$\begingroup\$ No - I don`t think so. What is the feedback signal - produced by the feedback element(s) ? Answer: It is the VOLTAGE across the resistor as part of the voltage divider which consists of C and R. \$\endgroup\$
    – LvW
    Mar 19, 2022 at 9:52
  • \$\begingroup\$ And what happens if I consider the power across the resistor to be my output? \$\endgroup\$
    – Abel
    Jul 19, 2022 at 2:46
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The simple voltage follower built with an op. amp as shown in figure below requires no external feedback elements:

Voltage Follower

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    \$\begingroup\$ Of course it requires an external feedback element...a wire. \$\endgroup\$ Jun 3, 2020 at 16:45
  • \$\begingroup\$ Ok. Very, very low resistance... Everybody happy. \$\endgroup\$ Jun 3, 2020 at 16:54
  • \$\begingroup\$ And of course the voltage follower will also work with a more significant resistance in the feedback path. The confusing part about your answer is that when you say "no...elements" you could mean either an open circuit or a short circuit. \$\endgroup\$ Jun 3, 2020 at 16:56
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    \$\begingroup\$ "no... elements you could mean either an open circuit or a short circuit..." This not apply. The attached figure eliminates any confusion. \$\endgroup\$ Jun 3, 2020 at 17:04
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    \$\begingroup\$ I never claimed that "there's no feedback". Just no use of discrete external components. Just to not being pedantic at all. \$\endgroup\$ Jun 3, 2020 at 17:29
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Feedback circuit or closed loop(as named in control theory) is used in control systems to know what happens in the output of system, and report that to the input and elaborate an input signal according to that!

So for your question the only element in the feedback is the capacitor. In the control community it is common to not use any feedback elements, but the wire is mandatory. It's called unit feedback.

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