Hi,
I have a INA125U connected to an light detector. The detector is reading a pulse from an LED emitter. I'm attempting to amplify the signal 18.3X using a 4.2Kohm resisitor for Rg. Schematic is attached, Rg is labeled incorrectly as a 15K so please ignore that. I have tried several different gain resistors and I don't get much if any change in the Output. I have also tried 3 different Amplifiers, all hand soldered. I have verified the Rg traces connect to the INA125, but it behaves as if they don't.
I have a very similar circuit using a INA122u that is working properly. The only difference is the sleep pin and the link for the Precision reference. I need to get the INA125U to the same approximate level of amplification, the INA122 is using a 15K Rg. I would use the INA122 but I don't have any boards to mount it on yet.
Scope trace of the INA125 gain is 64 (Rg = 1K) Orange is +Input, Blue is Output. Output is 100mv/div:
Scope trace of the INA122U at a gain of 18.3 (Rg = 15K) Orange is +Input, Blue is Output. Output is 200mv/div:
What am I doing wrong?