Feedback capacitor question (BJF design)

[the_floyd]

In this schematic:



... what is that 470pf capacitor doing? I'd assume it passes highs back into the NFB loop, ergo reducing the highs... but the filter it seems to form with the 3k resistor has a corner frequency of 112kHz, so I can't imagine that's actually what it's doing.  Could someone perhaps enlighten me as to what role it performs in the circuit? Help would be much appreciated.

[CynicalMan]

LTSpice is a great tool for questions like this. It makes a -2.5dB cut at 4.6kHz.



Link to the .asc file: http://sites.google.com/site/distorque/home/files/BJFDynaRed.asc

[the_floyd]

Ah, I see. I tried my hand at LTSpice not too long ago... too stupid to figure the program out, though. 

A big thank-you for the ASC file, I may take another crack at it now that I've got something to start with.

[CynicalMan]

No problem. Be sure to ask if you have any questions or issues.