I have this circuit which is acting with negative resistance. However when increasing the voltage well above saturation it produces a weird distortion on the output as seen below. can anyone explain.

enter image description here

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    \$\begingroup\$ What were you expecting? Is it significant that you're measuring part of the positive feedback loop, rather than the output of the opamp? \$\endgroup\$ – Heath Raftery Oct 10 '19 at 15:04
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    \$\begingroup\$ it produces a weird distortion on the output But... that's not the output that you're measuring. \$\endgroup\$ – user103380 Oct 10 '19 at 15:20
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    \$\begingroup\$ Look at pins 2 and 3 and compare the difference, If input and output voltages are in the linear CM range, then the output is linear, otherwise it is saturating the drivers (NPN Darlington high side and Common Emitter Darlington low side) Postitve Feedback cancels the negative feedback and increases the positive gain . Too much and it becomes a latch. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 10 '19 at 15:26

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