Digitally programmable second-order current mode continuous-time filters

The advent of differential voltage current conveyor (DVCC) has opened up new avenues in analog circuit design. However, a feature that is lacking in DVCC-based circuits is the non-availability of external control over circuit performance. To overcome this disadvantage, a new Digitally Controlled DVCC (DC-DVCC) has recently been proposed. In the present work, the DC-DVCC has been employed to design digitally programmable current-mode second-order continuous-time analog filters. Parameter tunability is achieved by the use of a 3-bit digital control word. The circuit can realize multiple circuit transfer functions by choosing the appropriate input and output terminals. Additionally, the circuit parameters Q and ω₀ can be set orthogonally by adjusting the passive components. The biquadratic circuit enjoys low sensitivities to circuit components. The proposed circuits are amenable for monolithic integration by virtue of the fact that only grounded components are employed. Circuit simulations using PSPICE yielded promising results.