I'm trying to use the rail-to-rail instrumental amplifier AD623. Here the datasheet.
First experiment: AD623 set as a voltage follower. Gain = 1 obtained by removing the Rg resistance between Rg- and Rg+ pin.
Everything goes right until I reach 4.3 V (read with VM1 and VM2) 4.3 V is the maximum amplifier output even when the difference between inputs is 5V. But this is a rail-to-rail amplifier...
Second experiment: AD623 set with gain = 2 (using a 100K resistor in according to datasheet).
Everything goes right until I reach 2 V of difference between inputs.(read with VM1) In this case 4.0 V is the maximum amplifier output.
Under this value the amplifier works good (if in input I have 1V in output I read 2V)
- +Vs = +5V
- -Vs = GND
- REF = GND
How is it possible?
Can anyone help me?
Thanks for help (and sorry for my poor english)