CMOS analog neural network systems based on oscillatory neurons

The authors discuss the design of two neural network systems based on the use of pulsing neurons. Each neuron was built as a simple voltage controlled oscillator (VCO) whose control voltage made the circuit oscillate or not oscillate. The interconnecting synapses between neurons are made with programmable transconductance amplifiers. The weight of each synapse is represented by the transconductance gain of the amplifiers, and is externally adjustable for each synapse. The oscillatory neuron circuit and the interconnection strategy for oscillatory neurons are described. Using this technique a 5-neuron Hopfield network and 6-neuron bidirectional associated memory (BAM) network were built and tested, using standard 2-μm double-metal, double polysilicon CMOS (MOSIS) chips