High dynamic range 2-TFT amplified pixel sensor architecture for digital mammography tomosynthesis

On-pixel amplifiers in amorphous silicon (a-Si) technology are an attractive replacement for industry standard on-pixel switch architectures in active matrix flat panel imagers in order to meet the low noise requirements of low-dose digital imaging modalities such as x-ray fluoroscopy and, more recently, 3D mammography tomosynthesis. However, implementing a-Si pixel amplifiers requires high-performance thin film transistors (TFTs) that are relatively large in size. In this research, a novel high dynamic range amplified pixel architecture using only two TFTs is introduced that is capable of amplifying the sensor value with a user controllable gain over a wide input range. Circuit operation and driving circuits required for on-pixel amplifier arrays are investigated, and simulation results are presented that indicate the feasibility of this pixel architecture for high resolution, low noise and x-ray tomosynthesis applications.