The accuracy and scalability of continuous-time Bayesian inference in analogue CMOS circuits

This paper discusses the idea of Bayesian inference in factor graphs implemented as continuous-time current-mode analogue CMOS circuits using Gilbert multipliers for arithmetic operations. The computational accuracy, accounting for the systematic and random (fabrication mismatch) errors, and the scalability of such realisations were verified in simulations of networks consisting of 5 - 121 nodes implemented using models from a standard 90 nm CMOS technology. The obtained results show a relatively short settling time, typically below 3 μs at a power less than 7 mW, with the equivalent computational speed of over 35 arithmetic operations per nanosecond but with a limited accuracy, mainly affected by fabrication mismatch. Such realisations could be used in applications requiring fast and low power approximate Bayesian inference.