A wide-dynamic-range programmable synapse for impulse neural networks

A fully-analog synapse circuit for impulse neural networks is described. The circuit is programmable over a dynamic range of several orders of magnitude. It is essentially a programmable switched-circuit source which incrementally contributes to the excitation of an impulse neuron. Shared-floating-gate FETs are used to implement a programmable current mirror exhibiting a nonvolatile storage characteristic. The synapse connection strength is modulated by incrementally adding or removing charge on the shared floating gate. A wide dynamic range is achieved through biasing the circuit to operate in the subthreshold region