Programmable neural logic

Abstract

Circuits of threshold elements ( Boolean input, Boolean output neurons ) have been shown to be surprisingly powerful. Useful functions such as XOR, ADD and MULTIPLY can be implemented by such circuits more efficiently than by traditional AND/OR circuits. In view of that, we have designed and built a programmable threshold element. The weights are stored on polysilicon floating gates, providing long-term retention without refresh. The weight value is increased using tunneling and decreased via hot electron injection. A weight is stored on a single transistor allowing the development of dense arrays of threshold elements. A 16-input programmable neuron was fabricated in the standard 2 μm double - poly, analog process available from MOSIS. A long term goal of this research is to incorporate programmable threshold elements, as building blocks in Field Programmable Gate Arrays.