Hello, I am designing an instrumentation amplifier using the current balancing amplifier architecture. The differential voltage at the input is copied to the sources of the input pair and generates a current through the resistor R1. I am running a noise simulation to obtain the output noise at the terminals of R1 which, for the specific circuit, is approximately equal to the input-referred noise. However, the resulting noise generated by the resistor R1 is much smaller than the predicted 4kTR by several orders of magnitude. On the contrary, it appears to be proportional to 1/R1. I am not sure I can understand how increasing the value of a resistor reduces the noise generated at its terminals...
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