Low Fixed Pattern Noise Current-mode Imager Using Velocity Saturated Readout Transistors
Zheng Yang; Gruev, V.; der Spiegel, J.V.
Circuits and Systems, 2007. ISCAS 2007. IEEE International Symposium on
Volume , Issue , 27-30 May 2007 Page(s):2842 - 2845
Digital Object Identifier 10.1109/ISCAS.2007.378764
Summary:This paper described a novel current-mode active pixel sensor (APS) imager. Conversion of photodiode voltage to output current is done using transistors operating in velocity saturation region. The high output impedance of this region makes it more suitable for current-sourcing operation than the linear region. The transistors also exhibit high linearity, allowing us to suppress fixed pattern noise (FPN) by correcting for both offset and gain variations among pixels. Experimental results on the fabricated 110times200 pixel array are presented. With conventional correlated double sampling (CDS), FPN is reduced from 3.8% to 0.85%. Further reduction requires compensation of gain variations, and results in a final FPN of 0.19%. A triple sampling approach is introduced to implement the described correction in hardware.
View citation and abstract |