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I am trying to simulate a wheastone bridge amplified with an AD8422. In principle, with a Rg of 500 ohm, it should give me a gain of 40, according to $$ G = 1 + 19.8k\Omega/R_G $$ but instead I get a gain of 0.45.I checked the circuit several times but I cannot see what I am doing wrong. It's the first time I simulate with LTSpice, but I don't think the error will be related with the program. LTSpice simulation

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  1. The input operating voltage range for the AD8422 is from \$-V_{s} + 1.2\ {\rm V}\$ to \$+V_{s} - 1.2\ {\rm V}\$. Your input voltages are about 50 and 200 mV, which is too low.

  2. Your plot doesn't show the differential input voltage to the in-amp, it just shows the voltage relative to ground of one arm of the input.

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