Four-input one-output voltage-mode universal filter using simple OTAs

This paper presents a new electronically tunable voltage-mode universal filter with four-input one-output employing six simple operational transconductance amplifiers (OTAs), two grounded capacitors and two MOS resistors. The use of grounded passive components is beneficial for integrated circuit implementation. The proposed filter can realize low-pass, band-pass, high-pass, band-stop and all-pass filtering functions without active and passive component-matching conditions and inverting-type input signals requirements. The natural frequency and quality factor can be tuned independently and electronically by adjusting the bias currents. The voltage-mode filter offers the features of high-input impedance and low active and passive sensitivities. The characteristics of the proposed universal filter are verified using PSPICE simulators through 0.35μm CMOS process. Experimental results are used to confirm the workability of proposed circuit through LM13600 commercially available OTAs. Also a digitally programmable filter is shown to confirm the advantage of multiple-input universal filter.