A temperature compensated array of CMOS floating-gate analog memory

Floating-gate transistors have been extensively used as analog memory elements in adaptive learning and neural systems. However, conventional techniques for storing and programming sub-threshold currents on floating-gate transistors are sensitive to temperature variations thus limiting their applicability to controlled environments. In this paper, we propose a temperature compensated floating-gate array which can be used to store and program currents down to nanoampere level. The core of the proposed current memory is a dual-channel floating-gate transistor based current reference circuit which uses a linear resistor in translinear loop. As a result the stored current is linearly proportional to the charge on the floating-gate and hence can be precisely programmed. The paper presents results from a prototype fabricated in a 0.5-μm CMOS process which validates the functionality of the proposed current memory cell.