A novel MOS compatible light intensity-to-frequency converter suited for monolithic integration

A novel circuit for light intensity-to-frequency conversion (LFC) suited for monolithic integration in MOS technologies is presented. The function is based on an R~S~ flip-flop whose toggle frequency is controlled by the discharge of a capacitance at the inputs of the R~S~ FF. For homogeneous illumination, the output frequency is proportional to the incident light level. For an implemented device, a dynamic range of more than six decades (approximately 0.2 lux up to >2/spl times/10/SUP 5/ lux) and a range of linearity of five decades were found.