Here's the reference circuit for amplifying the signal from a load cell with precision OPAMPs as per the MAX44248 datasheet. Can this OPAMP circuitry be explained please. What's the relation between the difference of the two load cell terminals (Vcell) and the ADC differencial input (Vin+ - Vin-)?

MAX44248 load cell amplifier



1 Answer 1


That is just the input stage to an instrumentation amplifier. The voltage across \$R_g\$ is the difference in voltage between the two corners of the load cell, thus you know the current through \$R_g\$

Knowing that number, and knowing that the same current must flow throuh both \$R_F\$, you can calculate that the difference in voltages between the op amp outputs will be $$ \Delta V \left( 1 + \frac{2R_F}{R_g} \right) $$, where \$\Delta V\$ is the difference across the corners of the load cell.

The advantage is that you can change the gain by changing one resistor, \$R_g\$. You might have to do some work to figure out what the effect of mismatched \$R_F\$ does.


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