Unified active filter biquad structures

The authors present a new biquad filter model based on nullators, norators, current mirrors and passive R (resistor) and C (capacitor) elements. Two implementations derived from the new biquad filter model by using second generation current-controlled conveyors (CCCIIs) and operational transconductance amplifiers (OTAs) are also proposed. The two biquad implementations are capable of achieving five important filter performance parameters simultaneously and without trade-offs, including universal filtering, minimum components count and independent control of ωo and ωo/Q. This is unlike recently reported filter structures which make certain trade-offs that emphasise some parameters at the cost of others. Simulation results are included confirming the theoretical prediction.