Five-inputs single-output voltage mode universal filter with high input and low output impedance using VDDDAs

The design of analog filter using active building block has been gained significant attention and has become an interesting research topic. A five-inputs single −output voltage-mode universal biquadratic filter using active building block, namely voltage differencing differential difference amplifier (VDDDA) is presented in this paper. The proposed filter consists of two VDDDAs and two grounded capacitors. The presented circuit has high impedance for all input voltage nodes and low impedance for output voltage node which is ideal for cascade in voltage-mode circuit without the use of buffer circuits. It can provide five output voltage functions which are band-pass (BP), low-pass (LP), band-reject (BR), high-pass (HP) and all-pass (AP) responses. For high-pass and band-pass functions, the inverting and non-inverting response can be achieved. The matching condition, the inverting and double gain amplifier are not required which is easy to select the output response by digital method. The natural frequency and quality factor can be electronically tuned that is attractive for microcomputer or microcontroller controllability. To verify the validity of proposed filter, the PSPICE simulation and experimental results using VDDDA constructed from commercially available IC are included. The measured results agree well with theoretical expect.