Active Pixel Sensing Circuit with Shared Amplifying TFTs for Improving Uniformity and Reducing Pixel Area

An amplifying TFT shared active pixel sensing (APS) circuit was proposed in this paper. For adjacent six APS pixels, only one amplifying TFT is used, and each sub-pixel has different switching TFTs. Then, the number of TFTs within a single pixel is reduced from 3T to 1.5T. The outputs of the six pixels are directly related to the characteristic of one amplifying TFT, hence uniformity is improved. As more space is left to locate the amplifying TFT, the charge-to-current gain can be increased and uniformity is further enhanced. SPICE analysis shows that, thanks to the proposed amplifying TFT shared APS scheme, the charge-to-current gain reaches 38.4 µA/pC, which is increased by 42% compared with other works. And the non-uniformity is reduced to 0.04%, while the non-uniformity is 23.78% for the conventional 3T-1 CAPS circuit.