Impact of random telegraph signal in CMOS image sensors for low-light levels

Abstract

This paper presents the investigation of fluctuating pixels resulting from the Random Telegraph Signal (R.T.S) of the source-follower transistor. The work takes into account the impact of the source-follower noise power spectral density (P.S.D) dispersion through correlated double sampling (C.D.S) readout circuit used in CMOS active pixel image sensors. The results allow the determination of the output r.m.s noise versus R.T.S noise characteristics. The distinctiveness of the observed flickering pixels is discussed in detail and the proposed mechanisms behind the phenomena are viewed in light of the collected data. We show that R.T.S noise main parameters dispersion of the source-follower transistor is a major factor influencing the circuit output r.m.s noise value distribution in a pixel array. Results are compared with experimental data. © 2006 IEEE.