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ADA4528 for thermocouple amplification

Question asked by julien44 on Jun 25, 2015
Latest reply on Jun 29, 2015 by julien44

Hello,

 

in the Application Note AN-1114, I saw an instrumentation amplifier built with ADA4528. I'm very interested about this circuit (especially about the auto-zero capability). My problem is that it can output a negative voltage, and I don't want negative voltage at output, to avoid destroying my ADC (I want my ADC to convert only positive voltages, to have my 24bits dedicated only for positive voltage).

 

The point is: if I add a clamp amp (as OPA698 from Texas Instruments, or AD8036 from AnalogDevices), I add an offset. So my circuit is not an auto-zero anymore. I saw a Single-Supply circuit, but I think it won't fit my application: if i understand well, a zero at the input will result in a Vs/2 output (Vout = Vin * Av + Vs/2).

 

How can I do to have an instrumentation amplifier giving me only positive voltages (Vout = Vin * Av), with the auto-zero capability ?

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