SYNAPTIC ELEMENT INCLUDING WEIGHT-STORAGE AND WEIGHT-ADJUSTMENT CIRCUIT

A weight-storage and weight-adjustment circuit includes a first hot electron injection device coupled to a first floating gate and a second hot electron injection device coupled to the second floating gate. The floating gates are associated with two series connected MOS transistors. The first and second hot electron injection devices comprise gated lateral bipolar transistors. The weight may be decreased by injecting hot electrons from the first hot electron injection device onto the first floating gate to decrease the first analog voltage and increased by injecting electrons from the second hot electron injection device onto the second floating gate to decrease the second analog voltage. Circuitry are provided to periodically adjust the absolute voltage levels on the first and second floating gates to prevent them from becoming too negative over time. First and second electron tunneling devices are coupled to the first and second floating gates, respectively, to simultaneously adjust the voltages stored on the floating gates to keep them within a desired voltage range.