Finished building CFA3 Ver1.21 recently.But offset reading seems off ,about 0.8V relative to gnd and 0.2V after solving oscillating issue ,VO+ to VO- also high as 0.2V
and bias went huge bump when switching ss to zf with oscillation on scope.I was quickly solving the problem by pulling 600pf,20pf caps form the mentions in this thread.
After some wild goose chase then I noticed a slight difference between schematic and board silkscreen.R211,R222,161,R262 value at current mirror is 680ohms but showing 300ohm on PCB.
now I have about 40mV offset w/o servo at each side with 680ohm resistor,haven't done any further test but I think I can have a good sleep tonight
Scrolling through the thread and it seems nobody mentioned .Not sure if that's a issue but just a heads up