Electronically tunable high-input impedance voltage-mode universal biquadratic filter based on simple CMOS OTAs

This paper describes a new electronically tunable three inputs and single output voltage-mode universal biquadratic filter based on simple CMOS operational transconductance amplifiers (OTAs) and grounded capacitors. The proposed configuration provides lowpass, highpass, bandpass, bandstop and allpass voltage responses at a high impedance input terminal, which enable easy cascadability. Additionally, the circuit parameters ω o and Q can be set orthogonally by adjusting the transconductances and grounded capacitors. The filter also offers an independent electronic control of parameters ω o by adjusting the transconductance through the bias current/voltage of the OTA. For realizing all the filter responses, no critical component matching condition is required, and all the incremental parameter sensitivities are low. PSPICE simulation results are performed to confirm the theoretical analysis.