Ralph Etienne-Cummings, Jan Van der Spiegel, Paul Mueller, Dept of Electrical Engineering, Southern IIlinois University, Carbondale, Illinois 62901, USA.
Neuromorphic systems have been primarily implemented using analog sub-threshold CMOS circuits primarily because the physics of sub-threshold operation and biological signal processing are identical. The effects of attempting to model biology accurately, coupled with the slow dynamics of sub-threshold MOS circuits, have prevented these systems from capitalizing on the main benefit of silicon which is its speed. Therefore the full potential of the silicon medium will be realized when neuromorphic systems are implemented with mixed signal circuits, where the essence of the biological computation is implemented with circuits which are best suited for the task. Presented are three hybrid systems, which realize the philosophy that the optimal neuromorphic VLSI circuit is one which imitates biology only when it is advantageous, uses sub-threshold circuits when speed is not required, and otherwise uses mixed signal strong inversion circuits.