Digital output silicon optical sensors

For the first time, a detailed description of low cost new intelligent (or smart) two-terminal optoelectronic devices without any on-chip circuitry for signal processing is presented. The design of the devices is based on the intelligent integration of micro-sized diodes and metal-oxide-semiconductor (MOS) capacitors. By combining physical processes and a functional voltage bias, such optical sensors transform the received analog input non-modulated optical signal directly into a pulse-width modulated electrical signal; the duty of the signal depends on the irradiation level, and the whole process is conducted without any integrated or external analog-to-digital converter. When the optical sensors operate under a pulsed irradiation synchronized with the functional voltage bias, unconventional logic properties are obtained that can be used to identify the emission from two equal LEDs.