Development of a Highly Sensitive CMOS Active Pixel Image Sensor

Abstract

CMOS image sensors with low power consumption and signal-processing circuits are widely used for mobile products and digital still cameras. A conventional MOS image sensor has high fixed pattern noise, up to the 30 mVp-p level, caused by the subthreshold voltage fluctuations of the cell-amplifier transistor and high random noises both the low-frequency cell-source follower circuits and the high-frequency output amplifier circuit. We developed and evaluated new circuit technologies to suppress both the fixed pattern noise in the pixels and the random noise in the cell-source follower and output amplifier. Using three kinds of analog circuit technologies, we developed an amplified 1/2-inch 1.3 M-pixel CMOS image sensor with low power consumption (60 mW) and high signal-to-noise ratio (50 dB).