An avalanche photodiode is read across a load resistor at room temperature

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

Measurement and Method, Ch Designing the measurement: noise, averaging, null and differential methods

Problem

An avalanche photodiode is read across a load resistor

R = 220\,\mathrm{k\Omega}

at room temperature

T = 293\,\mathrm{K}

, in a bandwidth

\Delta f = 25\,\mathrm{kHz}

. Its dark current is

I = 3.0\,\mathrm{nA}

. ((a)) Estimate the Johnson noise voltage of the load in this bandwidth. ((b)) Estimate the shot-noise voltage across the same load from the dark current. ((c)) Combine the two and state the total noise voltage.

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