Help me understand this negative feedback circuit

[Katerina]

negative resistance

This circuit works as negative feedback when R1=8K2 and positive feedback for R1=18K.
The graph is what I get for negative feedback at 200Hz. I don't get it why is split in parts and why if I change the amplitude of the input some parts in both directions dissapear.
For positive feedback I get smitch trigger I think..
Can you help me understanding this circuit?

 

[Katerina]

Re: negative resistance

I've done some progress with the circuit if anyone is interested. The non-linear areas of the graph are caused because of voltage saturation (also known as clipping) depended on the input amplitude. There is a maximun and minimum value of input signal to make the op amp work in the linear region.

If anyone has something more pls help.

 

[Ashtaroth]

negative resistance

actually the output voltage depends on the power suply.practically if you have Vcc +-15v then the maximun output voltage is Vcc-1=+-14volts before the voltage to saturate

 

[Katerina]

Re: negative resistance

actually the output voltage depends on the power suply.practically if you have Vcc +-15v then the maximun output voltage is Vcc-1=+-14volts before the voltage to saturate

You are right! In order to maintain the Kirchoff Law in the system!