Comprehensive filter design reference?

[bitrex]

In most of the EE textbooks I have, the topic of filter design seems to essentially be treated like "Here are some active filter topologies, and here are their normalized transfer functions, and here are a lot of tables of pole locations for say the 4 pole 1 dB Chebyshev filter. See you later." I'm wondering if anyone knows any good references, online or dead tree format, that I could use to get some insight into why the pole locations are what they are for certain filter responses?

 

[dlgoff]

There is a lot of info out there. Just Google "electronic filters" or "Active filters". There are some good chip manufactures application notes that might help like this one: http://www.national.com/an/AN/AN-779.pdf"