Anotace:
In recent years, the voltage differencing differential difference amplifier (VDDDA) has found its use in a variety of analog signal processing circuit designs. In this research, a second-order multifunction filter with multiple inputs and single output (MISO) voltage-mode using VDDDA as active elements is proposed. The structure of the proposed filter comprises two VDDDAs, two grounded capacitors, and two resisters. The proposed filter has a cascadability feature in a voltage-mode system as it produces voltage input and voltage output at high and low impedance ports, respectively. It can offer responses for all-pass (AP), band-reject (BR), band-pass (BP), low-pass (LP), and high-pass (HP) filters without additional inverting and double gain amplifiers, as well as the matching conditions. By choosing the appropriate input signals, these five filter responses are provided in the same circuit topology. With two VDDDAs, the bias currents can be utilized to electronically tune the natural frequency (0) in a manner independent from the quality factor (Q). Simulated and experimental results using readily available commercial ICs have supported the theoretical expectations and confirmed the practical operation of the proposed universal biquad filter.