I'm very interested in filter design and would like to learn more about them; however, I don't want to waste my time learning about them if there is no point. I already know the basics of filters and know how to use table etc to make particular filters. What I am wondering is, is there any justification for me to learn a lot about passive and active filters? These days, are there really any serious (not just a simple RC low pass) applications for passive and active filters or is it all DSP these days? I'd like to learn about it; however, if it's useless, then I think I'll go learn something else.

Could someone also recommend a good book?

I'm thinking: Filter theory and design: active and passive Adel S. Sedra, Peter O. Brackett

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    \$\begingroup\$ Much of the theory of DSP filter design is also applicable to analog filter design. There are also many things in analog circuit design that are not called "filters", but can be usefully viewed as such. For example, a solid understanding of filter design can help you guarantee stability in an amplifier. \$\endgroup\$ – Phil Frost Apr 17 '13 at 12:58
  • \$\begingroup\$ You ask two different questions: a) if there is a justification to learn a lot, and b) what book you should read. I recommend you to either edit out the book question (your question is getting voting to closed as not constructive), or ask a separate question for that. \$\endgroup\$ – user17592 Apr 17 '13 at 13:30
  • \$\begingroup\$ Would the book be informative about whether it's important to learn filters? \$\endgroup\$ – Andy aka Apr 17 '13 at 14:03

Before being digitized, all signals are analog. (in fact EVERYTHING is analog, digital world is just an abstraction level. But this is another story). Even if you do all the processing in DSPs, you always need, at least, an analog anti aliasing filter in front of the ADC. Or a reconstruction filter at the output of a DAC.

Thus it is useful.

But is it useful enough to spend a lot of time to become an expert? I don't know. If you are already familiar with standard filters design and if you know where to look if you need a tricky analog filter in the future, this is fine. You will learn it at the moment you need it.

  • \$\begingroup\$ Thanks for the answer. I'm aware that anti aliasing filters are need before signals go into A to D converters. Other than this, I know that filters are needed in high power application (like ladder ad latter filters). Aside from these two things, I don't really know of any other reason why an analogue filter would be used (and a complex one for that matter). \$\endgroup\$ – user968243 Apr 18 '13 at 2:17

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