Optimum configurations for single-amplifier biquadratic filters

Two new biquad circuits based on the Sallen-Key positive feedback structure are introduced and shown to be capable of realizing all possible second-order filter functions. The pole design equations and pole sensitivities are identical to those of the Deliyannis bandpass circuit which is the basis for the Friend biquad. The new circuits, however, display lower transmission zero sensitivities than the Friend notch realizations. Design details and experimental results are given.