Single VDDDA-based voltag-mode multifunction second order filter for analog signal processing

This paper describes the design of multifunction second order voltage-mode filter using the voltage differencing differential difference amplifier (VDDDA) as active element. The internal construction of VDDDA based on the 0.25um TSMC CMOS technology is used for simulation and testing. The proposed filter is sort of three inputs-single output (TISO) multifunction filter. It consists of single VDDDA, single resistor and two capacitors that is suitable to fabricate into monolithic chip. The filter can provide five standard functions namely, lowpass (LP), bandpass (BP), highpass (HP), band-stop (BS) and allpass (AP) responses, in the same circuit topology. Each filter response can be selected by digital method. The natural frequency and quality factor can be electronically tuned that is attractive for micro-computer or microcontroller controllability. The proposed filter was supplied by ±1.25 V source. The simulated results using PSpice simulation agree well with expected theoretical analysis.