Current-mode CMOS image sensor using lateral bipolar phototransistors

A current-mode image sensor has been designed using current mirrors with amplifying device ratios. Prototype sensors have been fabricated in a standard 0.18-(mu)m CMOS technology. Image capture is demonstrated from two 70 * 48 pixel arrays, using photodiodes and lateral bipolar phototransistors as the photodetectors. The latter type displays a reduced fixed pattern noise, while linearity is similar to that of the photodiode pixel. The lateral bipolar phototransistor pixels also show a greater response in the red region of the visible spectrum.