Ultra Low Voltage Class AB Switched Current Memory Cells Based on Floating Gate Transistors

A proposal for a class AB switched current memory cell, suitable for ultra-low-voltage applications is presented. The proposal employs transistors with floating gates, allowing to build analog building blocks for ultralow supply voltage operation also in CMOS processes with high threshold voltages. This paper presents the theoretical basis for the design of "floating-gate'' switched current memory cells by giving a detailed description and analysis of the most important impacts degrading the performance of the cells. To support the theoretical assumptions circuits based on "floating-gate'' switched current memory cells were designed using a CMOS process with threshold voltages V-T0n = \V-T0p\ = 0.9 V for the n- and p-channel devices. Both hand calculations and PSPICE simulations showed that the designed example switched current memory cell allowed a maximum signal range better than +/-18 mu A with a supply voltage down to 1 V, and relatively small device dimensions. In spite of the relatively large signal processing range, the class AB operation of the cell enabled a very low quiescent current consumption, 1 mu A in this design, resulting in a very high current efficiency and effective power consumption, as well as good noise performance.