Cascadable independently and electronically tunable voltage-mode universal filter with grounded passive components

In this paper, the voltage-mode universal filter employing the active building block, called voltage differencing differential difference amplifier (VDDDA) is introduced. The proposed circuit configuration has single output voltage node and five input voltage nodes. All input voltage nodes exhibit high impedance with low output impedance of the output voltage node, which is completely cascaded without the use of any external voltage buffer. The proposed filter realizes bandpass (BP), lowpass (LP), highpass (HP), allpass (AP) and bandstop (BS) filtering functions with using the same circuit topology. The output filtering response function can be obtained by appropriately applying input voltage without any matching condition. The control of the natural frequency and the quality factor can be done electronically and independently. The proposed circuit comprises three VDDDAs, two grounded capacitors and single grounded resistor. The workability of the proposed filter is investigated via PSpice simulation program and experimental results. The results agree well with theoretical anticipations.