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AD8129 output supply voltage

I designed a differential current-to-voltage output circuit with AD8129, but now the circuit output voltage is always 12V(positive supply voltage).

Input 1:differential current 20mA (IN+ minus IN-)

Input 1:differential current 10mA (IN+ minus IN-)

out voltage is always 12V

This is my  schematic.

  • Hi alec,

    With the gain that you're using (~4.3 V/V), it's better to use AD8130 not AD8129. AD8129 minimum stable gain is 10 V/V.

    Can you try increasing your gain (by raising R746 (3.3k)) to see if the output behavior improves? It's unlikely but could be that you are seeing some instability because you're below the minimum stable gain of the part?

    Also, I don't think I follow your "Input 1" definitions? Is a voltage applied to the inputs or current and in what fashion? It's better if you describe better how you're driving the inputs.