In this paper, a CMOS image pixel with a wide dynamic range and adjustable signal swing has been proposed by merging linear and logarithmic pixel operations. This merged pixel has proper sensitivity in dark environment by operating as a linear-type Active Pixel Sensor (APS), while it automatically switches to logarithmic mode after linear operation being saturated. This pixel gives a wide dynamic range more than 120dB, combining an integration type linear operation of the photodiode in the reverse bias and logarithmic operation in the forward region. In the logarithmic mode, this sensor is free from the threshold voltage variations due to the fact that it uses photodiode in forward bias region. In the linear region, conventional Correlated Double Sampling (CDS) method can be employed to suppress the Fixed Pattern Noise (FPN). The proposed pixel can increase the signal swing by adjusting a reset voltage level. The pixel size of 8.6um x 8.6um with a fill-factor of 29% has been designed using a 0.35um 4-metal double-poly standard CMOS process.
