Open-source floating-gate cell for analogue synapses

The floating-gate transistor is commonly employed as a non-volatile memory device, leveraging a floating node at its gate to store electrical charge over extended periods. This stored charge effectively alters the threshold voltage of the transistor. Utilizing standard CMOS technologies, floating-gate transistors can be designed and fabricated using conventional CMOS processes. This study focuses on characterizing the performance of a PMOS-based floating-gate transistor, specifically fabricated using the open-source Skywater 130 nm process. The modulation of charge on the floating node is explored through both hot-electron injection and Fowler–Nordheim tunnelling, providing insight into the resolution of these programming mechanisms. Additionally, the study includes a preliminary analysis of the retention time of the programmed charge in these devices. This work contributes to the open-source electronics community by detailing the design and programming techniques of floating-gate transistors developed with an open-source process design kit, and makes the corresponding FG cell designs available for public use.