Noise generated from components

Discussion in 'General Electronics Chat' started by Dritech, May 2, 2016.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    Hi all,
    Is there a general frequency range for the noise generated by components?
    Let's say that I have a circuit which process signals at frequencies lower than 400Hz. The output must contain the least possible noise.
    The best option is to use now-noise components, but unfortunately that is not always possible to find with specified requirements.
    Can the noise generated by the processing components be safely attenuated using a low-pass filter?
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
    Yes, as long as there is no signal in that frequency range that is near the same intensity as the noise. And, if noise is so important - noise generated by the components themselves, how will you add additional filtering components and not add more noise?

    I think we need a clearer definition of noise for your project - what is the signal source (impedence, waveform, sensor (input stage) and what type of circuit and concerns do you have in processing that signal (amplification, end use, ...).
  3. OBW0549

    Well-Known Member

    Mar 2, 2015
    Yes. In principle, it's from zero to infinity; in practice, there are bandwidth limitations that arise from such things as a device's intrinsic shunt capacitance or the unavoidable parasitic capacitance in circuit wiring. But these bandwidth limits are usually at frequencies far higher than we're interested in, and for most purposes the noise spectrum of resistive noise goes from "DC to daylight."

    Yes, that's the usual way, with the cutoff frequency of the low-pass filter set to just above your highest signal frequency of interest. Usually we boost the signal level first with a low-noise preamplifier and then apply filtering; this reduces the effect of any noise contributed by the filter itself.

    Here are some references that may (or may not) be useful:

    Low-Noise Signal Conditioning for Sensor-Based Circuits
    Fundamentals of Low-Noise Analog Circuit Design
    Dritech likes this.