RR additional material V1-3
Vol 1-3 Dr. Ramkumar Ramaswamy wrote a nice article for Linear Audio "A universal Continuous-Time active filter", Vol 1, pp 77. I had an intersting discussion with Ramkumar about the meaning of the "Characteristic Frequency" of a filter. As a follow-up, Ramkumar has written On the Characteristic Frequency of a Filter . This article is available online.