An active circuit for elliptic-type filters

An active filter circuit is presented that realizes second-order stages of band-reject fiters of all types, and low-pass, high-pass, and bandpass filters of elliptic and inverse Chebyshev types. The circuit is comparable in complexity (having either one more or one less resistor depending on the mode of operation of one op amp) and in sensitivities to the popular biquad circuits that realize all-pole low-pass prototype filters.