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AD623 powered with single supply change its gain

Category: Hardware
Product Number: AD623

Hello, I need to develope a low power project with an instrumentation amplifier, that's why I chose the AD623 model, cause it's rail to rail and I can power it using a low-voltage single supply, however, I'm having some problems using the amplifier. The thing is that it keeps its gain until it reaches 1.4V at the output. If it increases it changes its gain until it saturates.

I've been powering the AD623 with a 3.3V supply and connecting the REF pin to GND. I've also tried to put 1.65V on the REF pin and also powering it with 5V and I still having the same problem at the same output voltage.

I attatch images of the circuit I used to test the amplifier and the results I got. I use a potentiometer in the input to change the values of the input voltages.

This is the circuit that I use to test the amplifier. The gain it should be over 10.09 constant.

With this configuration I get this graphic

If I connect the REF pin directly to GND I get this

And if I power the amplifier with 5V and the REF pin to GND I get this.

If I use a dual supply of +/-3.3V the problem disappears and the amplifier works perfectly, however I can't use a dual supply on my project.

I hope you could help me.

Thank you so much in advance.

I write the gain of the configuration
[edited by: Hergue00 at 10:28 AM (GMT -4) on 27 Apr 2023]