ABSTRACT
Continuous-time active filters are active networks with characteristics that make them useful in today’s system design. Their response can be predetermined once their excitation is known, provided that their characteristic function is known or can be derived from their circuit diagram. Thus, it is important for the filter designer to be familiar with the concepts relevant to filter characterization. The filter network is considered to be lumped, linear, continuous-time, time invariant, finite, passive, or active. The chapter distinguishes the filters according to their frequency response as lowpass, highpass, bandpass, bandstop, allpass, and arbitrary frequency response. Filter design involves three separate processes or steps, namely analysis of circuits, curve approximation, and synthesis of the filter. Filter stability has been mentioned with reference to the pole positions of the filter function. In practical terms, the output voltage or current of a filter must always follow the input at steady-state, i.e., it should not become uncontrollable.
