An amplifier feeding a DC bridge readout has a one-sided voltage noise power density…

PHYSICS · Multi-part · Fermi University Physics · Electronics, Instrumentation & Communication · Feedback, operational amplifiers and analogue signal processing · Feedback, operational amplifiers and analogue signal processing

Inside the Instrument, Ch Low-noise front ends and noise measurement

Problem

An amplifier feeding a DC bridge readout has a one-sided voltage noise power density that follows

S(f) = e_{n0}^2\left(1 + \dfrac{f_c}{f}\right)

, with white floor

e_{n0}

and

1/f

corner

f_c = 100\,\mathrm{Hz}

. ((a)) By what factor does the noise power density exceed the white floor at

f = 1\,\mathrm{Hz}

(a DC-like measurement)? ((b)) By what factor does it exceed the white floor if the bridge is instead excited at

f = 2\,\mathrm{kHz}

, so the signal appears in a narrow band there? ((c)) What is the resulting improvement factor in rms noise voltage when moving the measurement from (a) to (b), for the same narrow bandwidth?

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