I did some more work on it and made it a peak detector. I never much liked having to use trim pots, which usually means that the circuit isn't self bias correcting, and can easily get out of adjustment.
Added a 3nF cap to the circuit output, and some resistance to the positive supply, here a 100K resistor. Also a 270K resistor to the + input of the op-amp, which also has a 910 ohm resistor to ground, used to minimise the error caused by the input bias current. Found that another resistance to the positive supply, a 270K resistor got the circuit in the sweet spot of detection. I think that these resistors are making up for the fact that my op-amp power supplies are not exactly the same absolute value voltages, and for the AGC line IF amp bias circuit. And it's not at all fussy, varying supply voltages doesn't mess it up. Substantially self biasing. I kept the 2nd diode, it acts like a catcher for the op-amp's output pin so it doesn't have to slew back so far when it comes time to rectify again .
12-07-2016, 10:04 AM
Hybrid Mode
