Mfg specs for noise analysis of op-amps only consider resistive inputs in their analysis. Example: Inverting amp config, input resistance R1, feedback resistor Rf. Input voltage noise Vn is typically calculated (in V/rtHz) as:Vn² = En² + 4kT(R||) + In²(R||)²where En and In are the voltage and current noise respectively of the op-amp, 4kT is the Boltzmann thermal noise coefficient, and R|| is the effective resistance of the circuit, R|| = R1Rf / (R1+Rf).Question: suppose, instead of R1 on the input, we have an impedance Z1 = R1 + i2πf L1, where L1 is an inductor, and f is a characteristic frequency. What then is the system input noise for the inverting amp config?I suppose it's Vn² = En² + 4kT(R||) + In² * abs(Z||)² , where R|| is as defined above, and Z|| = Z1Rf / (Z1+Rf). I justify using R|| for the thermal noise term b/c the inductor doesn't generate noise, but I'm not sure my logic is entirely correct.Any thoughts (and links) are appreciated. Thanks!

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It's not quite correct. The inductance in series with R1 is going to attentuate the voltage noise from R1. Since it is inductive, the attenuation goes up with frequency.A SPICE simulation should easily prove this to be the case.

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