A Miso Electronically Tunable Log-domain Universal Biquad With Digital Programmability

摘要

A novel Multiple-Input-Single-Output (MISO) Log-domain Universal biquad is presented in this paper. The biquad realizes all the standard filter functions, that is, lowpass (LP), highpass (HP), bandpass (BP), band reject (BR) and allpass (AP). The features of the circuit are that: the quality factor and pole frequency can be tuned orthogonally via the DC bias currents: the circuit description is very simple, consisting of merely few exponential transconductor cells and 2 grounded capacitors. Additionally, each function response can be selected by digital method. Without any external resistors and using only grounded elements, the circuit is good for absorbing the shunt parasitic capacitances, varying the filtering parameters and is suitable for monolithic integration. Furthermore, the biquad being designed by log-domain technique offers all the advantages of the technique and has low sensitivity and improved linearity. Simulated results are obtained to prove the theoretical analyses.