Hello everyone. Sorry for my bad English.
I need some help with the instrumentation amplifier.
Look at the analog part of my scheme below.
I'm using 3-OpAmp scheme on MCP602 operational amplifiers (U1:A, U1:B, U2:A), filtered reference (U2:B), active filter(U3:A), single supply on ADP3303 - 3.3V, 1% resistors. But independently from value of the potentiometer RV1 gaine is always near "2". I have tried different reference voltage and other amplifiers. The same result on the breadboard and
board. What is wrong?
P.S. I understand that the discrete design for the instrumentation amplifier are not greet in our days,
and it is better to use something like AD620 or AD8220 , but this scheme is cheaper in terms of repair.