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

Abstract

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- $\mu \text{m}$ CIS process, features pixel-level amplification and achieves an input-referred noise of 0.5 erms− with a correlated double sampling period of $5~ \mu \text{s}$ and a row read-out time of $10~\mu \text{s}$ . The proposed structure also 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 $50~\mu \text{V}$ /e- to 1.6 mV/e- with a charging period from 100 ns to $4~\mu \text{s}$ . The measured characteristics of the prototype CIS are in a good agreement with expectations, demonstrating the effectiveness of the proposed techniques.