Independently tunable mixed-mode universal biquad filter with versatile input/output functions

Abstract

This paper presents an independently tunable mixed-mode (including voltage, current, transadmittance, and transimpedance modes, i.e. four modes) universal biquad filter using one fully differential current conveyor (FDCCII), one differential difference current conveyor (DDCC), two grounded capacitors, four grounded resistors, and two floating resistors, which can realize all four modes five universal filtering responses (lowpass, highpass, bandpass, notch, and allpass). The proposed biquad filter has versatile input/output functions which not only realize all four modes five universal filtering functions in single-input multiple-voltage/current-output (SIMO) type but also provide all of them in multiple-input single-voltage/current-output (MISO) type without changing the filter topology. The proposed circuit permits both independent tunability (for ω0 and ω0/Q) and orthogonal controllability (for ω0 and Q) by adjusting grounded resistors without control factors matching conditions. No floating capacitors are used, and all the active and passive sensitivities are low. Moreover, in some modes, the proposed circuit still maintains the following advantages for five universal filtering responses: (i) cascadable feature, (ii) no component-value constraints, and (iii) no need of extra inverting or non-inverting amplifiers. H-spice simulations with TSMC 0.18μm 1P6M CMOS process technology and experimental results validate theoretical predictions.