I am building an interface for a PT100 temperature sensor and I need an instrumentation amplifier.
I came across the INA122 which looked ideal, only one component to set the gain, single supply and rail-to-rail output swing.
For the inputs I have a reference voltage of 0.1V and a signal voltage that swings between 0.1V and 0.1384V. The output needs to be in the 0-1V range so the gain of the amplifier needs to be around 26.
Now I simulated this all on Proteus and it works great when the input is at 0.1384V giving a good 0.99V output. However down at an input of 0.1V I get an output of 0.33V, not the 0V I was expecting.
What gets me is that the data sheet says rail-to-rail output but it isn't. Is this an error with the Proteus simulation or just a limitation of the device?
I guess if I can't solve it with one this device I will have to level shift, amplify and then level shift back down, yuck.
Thanks for you help.