A two-stage instrumentation amplifier has an input stage of voltage gain and…

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 Noise sources and amplifier noise

Problem

A two-stage instrumentation amplifier has an input stage of voltage gain

A_1 = 300

and input-referred voltage noise density

e_{n1} = 4\,\mathrm{nV/\sqrt{Hz}}

, followed by a second stage of input-referred voltage noise density

e_{n2} = 20\,\mathrm{nV/\sqrt{Hz}}

. The two stages' noise voltages are uncorrelated, and the second stage's noise is referred to the amplifier's input by dividing by

A_1

. ((a)) Find the amplifier's total input-referred voltage noise density. ((b)) Find the percentage by which the second stage raises this density above

e_{n1}

alone.

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