[sdiy] ADC - anti-alias filter

Richie Burnett rburnett at richieburnett.co.uk
Fri Mar 24 21:06:04 CET 2017


As others have said, noise is broadband unless it is filtered somewhere. Without any filtering, all of the noise power will alias into the baseband when you perform your sampling and it will raise the noise floor of your measurement / recording.

In general you don't want the bandwidth of you amplifier to be any greater than it needs to be in order to capture all of the signal, otherwise it will just let through unwanted noise. And the wider you open the gate, the more noise that will flood in.

A recent commercial project I was working on used strain gauges for some wireless instrumentation. These had gains upwards of x4000, and although the strain signals themselves had a quite controlled and predictable bandwidth, the bandwidth of the amplifiers needed to be tightly controlled to prevent excessive measurement noise.

-Richie, 

Sent from my Xperia SP on O2

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