A photodiode preamplifier has a noise density referred to its input and a bandwidth

PHYSICS · Subjective · 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

A photodiode preamplifier has a noise density en=25 nV/Hze_n = 25\,\mathrm{nV/\sqrt{Hz}} referred to its input and a bandwidth Δf=20 kHz\Delta f = 20\,\mathrm{kHz}. The step between an illuminated reading and a dark reading is 0.50 μV0.50\,\mu\mathrm{V}. There is no drift. Averaging each of the light and the dark readings for the same time tt, find the value of tt needed to reach a signal-to-noise ratio S/N=10S/N = 10 on the step.

Browse the problem library