Problem with AD8293G80

I am trying out the AD8293G80 as a possible replacement for our current IA. The IA is used to amplify the output of a pressure sensor and pass the output to an A/D. I have hooked the AD8293 up as indicated in the data sheet but the output (either pin 4 or pin 6) reads 5.1 mV and doesn't change for any change in input. The input signal from the pressure sensor varies between 0 and 10 mV. The common mode voltage is about 2.44 V. The power supply voltage is 5V. I tried another AD8293 and got a similar constant output of 5.6 mV. The pressure sensor is working properly as is the A/D. Do you have any suggestions as to what might be wrong?

Thanks.

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  • Shifting the reference to allow negative offsets is a common practice and a typical application for this terminal. However, the reference terminal is not always a high-impedance input, as it is the case for AD8226. You can find an example on page 20 of the data sheet. Keep in mind that the picture shows OP1177, but this amplifier won't work if you want to buffer 200mV. I would try something like AD8505 instead.

    If by better way you mean you don't want to add an additional amplifier to buffer this voltage, AD8420 would help. You can introduce an offset without a buffer, but you just need to mind the resistor values into your total gain calculation, as shown in page 21 of the data sheet (look at figure 64).

    Regards,

    -Gustavo

Reply
  • Shifting the reference to allow negative offsets is a common practice and a typical application for this terminal. However, the reference terminal is not always a high-impedance input, as it is the case for AD8226. You can find an example on page 20 of the data sheet. Keep in mind that the picture shows OP1177, but this amplifier won't work if you want to buffer 200mV. I would try something like AD8505 instead.

    If by better way you mean you don't want to add an additional amplifier to buffer this voltage, AD8420 would help. You can introduce an offset without a buffer, but you just need to mind the resistor values into your total gain calculation, as shown in page 21 of the data sheet (look at figure 64).

    Regards,

    -Gustavo

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