I just listed through a complex 480 pages long book about op-amps, but I didn´t find this circuit.It is shown in few Fender amp schematics, it´s not connected in signal chain, but on the path to CA3080 in compressor circuit.
Can anyone tell me what is it good for, and why is it connected the way it is?
I have also plotted the in(greeen)/out(blue) curve.

 

Hi,

It's an inverter curcuit, but with positive feedabck, too. From the plot, it's got a very limited signal range. Seems like you can get inversion with gain by more predictible arrangements. Maybe it's Fender's way of making a circuit with a hard clip characteristic. Certainly going to alter the input signal.

 

Hi,

It's an inverter curcuit, but with positive feedabck, too. From the plot, it's got a very limited signal range. Seems like you can get inversion with gain by more predictible arrangements. Maybe it's Fender's way of making a circuit with a hard clip characteristic. Certainly going to alter the input signal.

I just found it out, I should never analyse circuits seperately. The output is connected to forward biased diode in bias circuit of CA3080, this "amp" changes current through it.

If you are interested, have a look at this thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=88297

 

Google "Howland current source".