i used two resistors in series. since nothing is connected to the node, total resistance is 5.4 kohm
This is strange. Somebody else had the same problem a month ago. See here: https://www.edaboard.com/threads/253558/And, the output is amplified by 2 * theoretical gain.
That's weird. David was getting double the expected output in simulations. Maybe you could email the manufacturer and ask for clarification / explanation?my problem is with actual circuit. simulation is fine.
I am giving signal from function generator, at positive input terminal. The negative input terminal is grounded.
If you were with the TI support stuff, how would answer the question?Maybe you could email the manufacturer and ask for clarification / explanation?
Try the opposite: Ground the pos. inpiut and apply the sgnal at the inverting terminal. Same result?
Or the real circuit is no corresponding to intended/expected one. I can confirm that INA128 is generally behaving according to the datasheet.either the measurement is wrong or the datasheet is wrong
With about factor 10 gain, the first stage output voltage is almost symmetrical, independent of input common mode to differential relation. Then output is about factor 1.5 high with floating REF pin, not factor 2.I suppose (hope) that the measurement will be according to the data sheet. In this case, the resistor in the last stage is not grounded.
With about factor 10 gain, the first stage output voltage is almost symmetrical, independent of input common mode to differential relation. Then output is about factor 1.5 high with floating REF pin, not factor 2.
I think, it's pointing in right direction. Which external circuit fault could achieve the observed gain?Sorry, my error. My way of thinking was a bit to simple (hopefully, in this case only).
but you're only checking the output, you'd think the gain is double.
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