High Dynamic Pixel Implementation Method for Adaptive Adjustment of Gate Voltage of Transfer Transistor on Chip

Abstract

In CMOS Image Sensors (CIS), high dynamics are required to adapt to the variation of light intensity in different application scenarios. In this paper, we propose a highly dynamic method based on an 8T active pixel, which can adjust the gate voltage of the transfer transistor on the chip adaptively by changing the gate voltage of the transfer transistor in the pixel, to adjust the height of the potential barrier between the PD and FD nodes so that the PD node inside the pixel can fuse the signals of long and short exposures. The output of the sampled pixels is compared with the reference voltage, and the result is output to the gate of the transfer transistor through the DAC to determine the total exposure time allocation, achieving the effect of adaptive adjustment of the exposure time allocation by the pixel output. Based on the 55 nm process, the proposed method is verified by a specific circuit design, and the validation results show that the full trap capacity is 24 ke− and the dynamic range can be extended from 66.02 dB to 89.54 dB without decreasing the pixel fill factor and increasing the signal processing complexity, and the long and short exposure times can be adjusted adaptively according to the application scenario to obtain the optimal high dynamic. The solution is optimized for high dynamics.