UV-activated conductances allow for multiple time scale learning.

Ultraviolet (UV) photoinjection of electrons through SiO(2 ) provides a convenient and simple method for programming analog, nonvolatile memories in CMOS circuits. The time scales involved in the UV programming process are well suited to multiple time scale learning algorithms providing several orders of magnitude in programming rate. The method requires no special processing technology. Measured characteristics of the UV photoinjection devices and experimental results from a synapse circuit built using these devices are presented. This synapse circuit includes a continuously adjustable weight, an electronic learn/hold control and slow forgetting dynamics, while allowing an unimpeded multiplication operation at all times.