Noise Analysis of a Current Mediated Active Pixel Sensor for Digital Imaging

Crystalline silicon active matrix imagers have gained prominence due to their highly integrated nature in digital imaging applications ranging from star trackers to monolithic integrated circuit cameras. In this project, the operation and noise performance of a pixel with current mediated readout (C.M.APS) is investigated. The total output noise power spectral density (PSD) is theoretically calculated using small signal analysis to obtain the noise contribution of each pixel component as well as the overall pixel noise transfer function. The theoretical work is compared to results obtained from a circuit simulated in stateof- the-art complementary metal-oxide-semiconductor (CMOS) 0.35pm technology using the Cadence integrated circuit design environment. Signal gain, noise, noise bandwidth and frequency response results are presented. Results indicate that, in contrast to a C.M.APS pixel operating in Direct Mode, a C.M.APS pixel operating in Difference Mode allows suppression of fixed pattern noise components without causing an increase in random noise components.