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Negative voltage on INA138 output

Other Parts Discussed in Thread: INA138

Hi all,

I am trying to sense a current range of 0 to 1.5A with a INA138. I have a 33mOhm shunt resistor to sense the current and I put an RL resistor of 5k in order to have a gain of 1 at the output.

I am testing that chip with an active load and drove it with a current of 1A. What I got at the output was -33mV. It seems that the INA138 is working, but there is an extra minus sign that I don't understand. I have soldered two identical circuits and it does the same thing.

I have tried to drive it with more current, but the result is the same. The absolute voltage is good, but it goes further towards negative scale.

Any ideas? Isn't it supposed to output a positive current through RL? Because what I see at the scope seems to be a negative current getting into the chip, which doesn't make any sense....

Thank you veru much!