Hardware implementation of an expandable on-chip learning neural network with 8-neuron and 64-synapse

An expandable on-chip learning neural network chip with 8-neuron and 64-synapse is designed and fabricated with a standard 0.6 μm CMOS technology. Large-scale neural network with arbitrary layers can be constructed by connecting unit chips. A novel neuron circuit with programmable parameters is proposed. It generates riot only the sigmoid function but also its derivative. The neuron has a push-pull output stage to gain strong driving ability in both charge and discharge processes, which is very important in heavy load situations. An improved Gilbert multiplier is also proposed. It has one end current output and precise zero point. The learning system itself can be used as a refresh tool to keep the weight value right. Experiment results show that it has good performance.