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Pros and Cons of analog and digital filters

Discussion in 'General Electronics Discussion' started by Mark2014, Sep 22, 2014.

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  1. Mark2014

    Mark2014

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    Sep 22, 2014
    I am interested in a simple comparison of analog & digital filters in general as to frequency response , hardware requirements, delay, limitations of both filters,....etc, and in general their pros and cons. I am much obliged if anyone can help me with this comparison or guide me to sources of such matter but rather simple detailed ones not the mathematical theory but only pros and cons and much of them and focus on the limitations of digital filters please.
    Regards and many thanks
     
  2. Gryd3

    Gryd3

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    Jun 25, 2014
    When you ask about filters, can you please clarify intended use?
    Are you talking about filters that may be used in an Equalizer, or are you talking about simple High-pass, band-pass, or low-pass filters.
    A 'Filter' could do many things.
     
  3. Laplace

    Laplace

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    Apr 4, 2010
    You should also clarify whether you mean FIR or IIR digital filters. But in any case digital filters won't be much useful for high-frequency RF filtering, or for power line noise rejection. But for signal processing purposes the following link may have some useful information. The first paragraph of the chapter is below:

    http://www.analog.com/static/imported-files/tech_docs/dsp_book_Ch21.pdf

    FILTER COMPARISON

    Decisions, decisions, decisions! With all these filters to choose from, how do you know which to use? This chapter is a head-to-head competition between filters; we'll select champions from each side and let them fight it out. In the first match, digital filters are pitted against analog filters to see which technology is best. In the second round, the windowed-sinc is matched against the Chebyshev to find the king of the frequency domain filters. In the final battle, the moving average fights the single pole filter for the time domain championship. Enough talk; let the competition begin!
     
  4. Mark2014

    Mark2014

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    Sep 22, 2014
    Thanks for your response. I am actually interested first in a theoretical comparison of filters(A & D) in general in simple terms, and second more into exploring the digital filters limitations and drawbacks.
     
  5. Mark2014

    Mark2014

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    Sep 22, 2014
    Thanks for the reference. An interesting point that you mentioned; that digital filters wont be useful for RF filtering. why? what about higher bands do digital filters work there? Please clarify this matter as i said i am interested in the limitations and drawbacks of digital filters and if u have other limitations please mention them. Thanks
     
  6. Laplace

    Laplace

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    Apr 4, 2010
    Digital filters require that the signal be digitized. There are limitations to how fast an analog-to-digital converter can be made to work. At some point in the RF spectrum no ADC will be able to convert fast enough.
     
    Mark2014 likes this.
  7. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Another few points to throw into the discussion:

    - Digital filters are (typicall) very stable, reproducible and (can be) precise depending on the stability of the clock and the accuracy of the filter parameters. Analog filters, on the contrary, have to deal with the inaccuracies of the components, temperature variations etc. They are therefore typically less accurate than a digital filter (exceptions prove the rule).

    - Digital filters deal with signals in a low voltage domain (a few Volts within the limits of the typical digital power supply, e.g. 5V, 3.3V). Analog filters can be designed to operate at much higher voltages and/or currents. For example a line filter inserted into the supply of a mains operated device, a filter inserted into the mains connection of a power-line communication device etc.
     
    KrisBlueNZ likes this.
  8. Mark2014

    Mark2014

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    Sep 22, 2014
    Thanks for your comments. One thing I forgot to ask, is what are the points that I should consider when comparing the two filters? I know of linearity, phase response, steepness between cut and pass ranges. If you can, please suggest others.
    Thanks.
     
  9. Gryd3

    Gryd3

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    Jun 25, 2014
    Intended purpose.

    Comparing filters with no intended purpose will result in a mess of theory crafted statements, ideas, and suggestions.
    It may be best to narrow down the whole Digital vs Analogue filter to something like 'Digital vs Analogue Filters in Audio'
     
    Harald Kapp likes this.
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