A circuit that creates a logarithmic response from an integrating CMOS pixel

A wide dynamic range (WDR) pixel has been developed that integrates the photocurrent for a time that depends on the photocurrent. A one-dimensional (ID) array of these pixels has been fabricated on a 0.35-μm 2P4M CMOS technology. These WDR pixels achieve improved low light sensitivity by incorporating an nMOS transistor between the photodiode and a floating diffusion formed by the source and drain diffusions of other pixel transistors. An off-chip logarithmic amplifier is used to generate a global reference voltage V_ref(t) to create a logarithmic photoresponse.