A lock-in amplifier's output filter is a single section (a per octave roll-off) with…

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

A lock-in amplifier's output filter is a single

RC

section (a

6\,\mathrm{dB}

per octave roll-off) with time constant

\tau = 2.0\,\mathrm{s}

. The demodulated signal has amplitude

500\,\mathrm{nV}

and the noise density referred to the same point is

8.0\,\mathrm{nV/\sqrt{Hz}}

. ((a)) Find the equivalent noise bandwidth of the filter. ((b)) Find the rms noise voltage at the output. ((c)) Find the amplitude signal-to-noise ratio. ((d)) Find the time needed for the filter's output to settle to within

1\,\%

of its final value after a step change.

Browse the problem library