A continuous-time varactor-based temperature compensation circuit for floating-gate multipliers and inner-product circuits

Floating-gate (FG) transistors are commonly used in synthetic neural systems for implementing analog multipliers. However, conventional floating-gate multipliers are sensitive to variations in temperature which limit their application to only controlled environments. Previously, we had reported an off-chip temperature compensation algorithm for floating-gate current memories which used varactors to cancel out the temperature dependent factors. In this paper, we report a continuous-time circuit implementation of the temperature compensation algorithm and show that it enables on-chip implementation of temperature compensated current amplifiers and analog multipliers. Using measured results from fabricated prototypes in a 0.5μm CMOS process, we demonstrate the functionality of the compensation circuit and show that it leads to an order-of-magnitude lower temperature sensitivity for FG multipliers when compared to an uncompensated case.