Active Pixel Cmos Image Sensor Design

With the rapid development of microelectronics, the process develops from sub- micron to deep sub-micron. The performance of CMOS image sensor has reached and even exceeded CCD's. CMOS image seneor becomes the focus of image sensor. Our project aims to design active pixel CMOS image sensor which is expected to be used in wireless sensor network.This design starts from the study of principal of photo-electricity conversion of photodiode. Then, the models of photodiode are established,the relationship figures of light intensity and photocurrent are achieved by using MATLAB, n+-psub diode is chosen as the device of photo-electricity conversion. According to the model, circuits are designed, which include the circuit of two kinds of pixel, column output circuit, output buffer and decoder that is used to select row and column.The pixel array is 16×16 and every pixel is 8um×8um. The photodiode in pixel is about 36 square microns. There are tow kinds of pixels, including basic active pixel and improved active pixel. It is proved by HSPICE simulation that dynamic range of improved active pixel is 80% times wider than basic active pixel's. The column output circuit is realized by double sample and hold circuit which can effectively decrease FPN (fixed pattern noise). Output buffer is realized by the feedback application of amplifier which can drive big load capacitor. The Av of amplifier is more than 70db, phase-margin of it is more than 70 degree, PSRR of it is more than 50db. I simulate the whole circuit by HSPICE and get the result that the output signal voltage is linear with light-intensity and the light dynamic range reaches to 9.5 W/square meters ( room illumination is about 0.1 W/square meters).