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I have no experience with current sensing ICs and I'm trying to build a current sensor with an INA138 IC that I've imported into LTspice. From the manufacturer's website, I'm expecting my output to correspond to:

$$V_o=I_sR_sR_L/5k\Omega$$

With an input current of 7.14mA I get \$V_o=143mV\$ instead of what I would calculate as \$V_o=284mV\$.

This is the datasheet where I got the configuration and \$V_o\$ derivation.

This is my circuit:

enter image description here

As far as I can tell my configuration and resistor values are all fine so I'm not sure why I'm having this issue with the measurements.

JRE
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p.chives
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1 Answers1

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As already mentioned in the comments, you mixed up the actual load with the \$R_L\$ in the formula. The datasheet explains the basic operation of the current sense amplifier:

The device converts a differential input voltage to a current output. This current is converted back to a voltage with an external load resistor that sets any gain from 1 to over 100.

So you can set the gain with \$R_L/5k\Omega\$. So a reasonable resistance \$R_L\$ would probably be in the range of 5k to over 500k. I'm not sure if you really want to attenuate the signal.

Lars Hankeln
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