MOS area sensor: Part II—Low-noise MOS area sensor with antiblooming photodiodes

The development of a high-sensitivity 320 × 244 element MOS area sensor and a novel fixed pattern noise (FPN) suppressing circuit are reported in this paper. The new device incorporates p+-n+high-C photodiodes and double-diffused sense lines. The p+-n+high-Cphotodiodes provide a large dynamic range and a large saturation signal of 1.4 µA with 6-1x W-lamp illumination. The double-diffused sense lines are introduced to vastly improve blooming characteristics, making use of a built-in potential barrier. FPN is proved to stem mainly from inversion charge variations through horizontal switching MOS gate capacitances. A simple high-performance FPN suppressing circuit is proposed which realizes high signal-to-noise (S/N) ratios of more than 68 dB at saturation. The new sensor is tested in a high-sensitivity black-and-white VTR hand-held camera and will find broad applications.