Multiple-input-multiple-output log-domain universal biquad filter

A simple log-domain technique based Multiple-Input-Multiple-Output (MIMO) universal biquad realizing simultaneously all the standard filtering functions viz; Lowpass (LP), Highpass (HP), Bandpass (BP), Bandstop (BS), and Allpass (AP) is presented in this paper. The biquad being designed by log-domain technique offers all its advantages. The circuit besides permitting independent electronic adjustment of pole frequency ( o) and the Quality factor (Q) is: simultaneously Single-Input-Multiple-Output (SIMO) and Multiple-Input-Single-Output (MISO), free from matching conditions, capable of absorbing the shunt parasitic capacitances, amenable for monolithic integration, composed of merely a few exponential transconductor cells and grounded elements. The other features of circuit are its low sensitivity and good linearity. Simulated and experimental results are obtained to prove the theoretical analyses.