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\omega_0gain-sensitivity products, theQgain-sensitivity products, and the\omega_0andQdeviations 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\omega_0deviation due to the amplifier's limited frequency response. In this expression, which applies for all active filters which have low\omega_0active sensitivities, the only configurationdependent quantities are theQgain-sensitivity products.