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In this question/answer theres this op-amp circuit:

enter image description here

I can't work out whats happening. At a glance the op-amp circuit looks like a cross between a schmitt trigger, differential amplifier and possibly an oscillator! Help!

What is it? What could ut be used for? How does it work? Please assume working knowledge of op-amps but not harder math such as calculus, transfer functions etc

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    \$\begingroup\$ Start by determining the transfer function for the op amp. \$\endgroup\$ – Ignacio Vazquez-Abrams Feb 25 '18 at 12:27
  • \$\begingroup\$ @Tony Stewart. EE since '75 you need to explain this circuit. Good luck! \$\endgroup\$ – Andy aka Feb 25 '18 at 19:44
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It's a diff amp comparing the fixed value off the offset / null and the value of the sensor. The two 2k resistors look like atlantic attempt at hysteresis but don't seem like very good values.

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Without going through the equations it’s hard to tell what’s going on with that circuit and which feedback branch dominates, but the only times I have seen similar things is when people make mistakes.

I once saw an electronics magazine publish a “non-inverting amplifier configuration” for audio applications that just mirrored the resistor location of the inverting one (thus creating a Schmitt trigger).

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