Low Noise Design Of Programmable Gain Amplifier For CMOS Image Sensor

Nowadays,Internet is highly popular and developed,all kinds of information can be quickly and widely spread through the Internet,so it is particularly important to obtain information quickly and accurately.As the most intuitive information source,image information is an important carrier of information transmission,so image sensor has been widely used in military,security,industry,automotive electronics,consumer market and other fields.So performance and stability of image sensor is very important in extreme environment.This paper takes the night vision image performance of CMOS image sensor as the starting point,aiming at the urgent need of improving the night image acquisition ability of image sensor under various application conditions,In order to realize the low noise design of PGA in a specific CMOS image sensor environment(5.94um),the noise situation of PGA is analyzed deeply,and circuit layout are designed and simulated deeply,Noise of PGA must lower than 150 uV Pixel noise.According to the special application environment of the column pre PGA in CIS,Considering the cost and low noise requirement,two-stage amplifier with higher gain and stability has to be abandoned.Using single-stage amplifier with cascade instead,and the switched capacitor array structure is used.The PGA system with 8X gain is designed completely.For layout design,It is another key point and an important part of low noise design of PGA.By analyzing circuit,the capacitor array is arranged before amplifier,and for matching requirements of the input of the differential pair in amplifier,common center matching structure is used.For the accuracy of the PGA gain,the switched capacitor array is specially designed in layout.In order to avoid the crosstalk caused by parasitic signal,the substrate and metal wire are isolated completely to reduce the crosstalk,and confirmed by post simulation.Combining with the actual application requirements and Huali 55 nm process,By optimizing circuit and back-end layout,The PGA is designed in the height of 5.94 um.The final length is 150 um,which achieves the expected design objectives.