A real novelty in the design of active filters might be to consider more than the bandwidth and the price of the op-amp(s) to be used. As an Applications Engineer of long standing I am not very skilled at designing active filters but I have very considerable experience in extracting skilled active filter designers from the pitfalls of not considering all of an op-amp's specifications. This lecture considers problems in active filters caused by lack of consideration of such op-amp parameters as bias current, voltage noise, current noise, Johnson noise, decoupling requirements, ability to drive capacitive loads, ability to tolerate capacitive feedback (almost zero in transimpedance op-amps), open-loop gain, slew rate and several others. It has nothing new to say about the design of filters, but discusses issues with which too many filter designers seem to be insufficiently familiar.