Sensitivity and frequency limitations of biquadratic active filters

A comparative study of single-amplifier filters, fifteen different two-amplifier circuits, and the state-variable three-amplifier configuration is given. The figures-of-merit used are the passive sensitivities, the gain-sensitivity products, the gain-sensitivity products, and the and deviations due to the amplifiers\´ limited bandwidth. In addition, practical matters such as input impedance and component spread are considered. Among the circuits considered a particular twoamplifier resonator emerges as the "best" biquadratic section. Some of the interesting results include a unified expression, applicable to a large class of low-sensitivity circuits, for the deviation due to the amplifier\´s limited frequency response. In this expression, which applies for all active filters which have low active sensitivities, the only configurationdependent quantities are the gain-sensitivity products.