A 0.5e_rms⁻ Temporal Noise CMOS Image Sensor With Gm-Cell-Based Pixel and Period-Controlled Variable Conversion Gain

A deep subelectron temporal noise CMOS image sensor (CIS) with a Gm-cell based pixel and a correlated-double charge-domain sampling technique has been developed for photon-starved imaging applications. With the proposed technique, the CIS, which is implemented in a standard 0.18-μm CIS process, features pixel-level amplification and achieves an input-referred noise of 0.5 e−rms with a correlated double sampling period of 5μs and a row read-out time of 10 μs. The proposed structurealso realizes a variable conversion gain (CG) with a period-controlled method. This enables the read-out path CG and the noise-equivalent number of electrons to be programmable according to the application without any change in hardware. The experiments show that the measured CG can be tuned from 50 μV/e- to 1.6 mV/e- with a charging period from 100 ns to 4μs. The measured characteristics of the prototype CIS are in a good agreement with expectations, demonstrating the effectiveness of the proposed techniques.