A CMOS ultraviolet (UV) light intensity to duty cycle converter with calibration circuits for monitoring environmental UV light applications

In this paper, a CMOS ultraviolet (UV) light intensity to duty cycle converter with calibration circuits for monitoring environmental UV light applications is innovatively proposed. In this work, a calibration technology is proposed to overcome the nonlinearity coming from the intrinsic internal resistors of operational amplifier (OP) and switch built by BJT. After calibration, the maximum linear error is decreased to 0.33%. The UV Index (UVI) ranges from 2 to 11, and the corresponding output duty cycle range is 68.68 to 73.37%. The chip area is 1.016 × 1.01 mm
²
. The proposed chip is suitable for wearable devices to monitor environmental UV light intensity.