I am using an INA333. I currently have no gain resistor (Av = 1) and running a 200mVp-p 150Hz sine wave into it. I am running single supply with 3.6V. I am finding that I must supply a Vcm on the input > 1.4V independent of Vref. For example if I set Vref = 1.6V and reduce Vcm below the ~1.4V threshold I get periodic partial cycles of sine waves with dead time between these cycles. The dead time is = Vref. This is occurring on a demo board with the part as well. I suspect it has to do with instrumentation amps and I don't understand them could you please explain? Ultimately my design will work with sensors like thermocouples where I will have no knowledge of the Vcm on the input (other than it is positive and below Vcc). In this instance I would like to configure the board where Vref = 0, the amp disregards the Vcm and measures the thermocouple voltage and I get full range for the A/D (ground to VCC).
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