Recently when I did my design using AD8676 as below circuit, when the pin2 of U37 start to rise, the pin1 of U37 went to around to 10V instead of ground, may I know why it behaviour let that?
It will never work. The AD8676 is rail to rail OUTPUT only, it is NOT rail to rail INPUT.
The inputs have to stay at least two volts from either rail. You could add a -5V supply
(not critical, -3 to -15V) or switch to an ADA4084-2.
thank you for reply, do you mean the either the pin2 or pin3 can't starting from 0V? because in my circuit, the pin3 is grounded and pin2 voltage is from 0 to 5.6V, it not touch the rail of +12V.
I said either rail. That means the plus rail and the negative rail, which in your case, is connected
If you look at the data sheet, for +/-5V operation, the input voltage range (IVR) is -3V to +3V.
So on ground and +12V, both pins 2 and 3 have to be between 2V and +10V.
So as I said before, it will never work. Connect pin 4 to -5V and try the circuit.
OR switch to the ADA4084-2.
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