Linear current mode imager with low fix pattern noise

A new imaging architecture with a linear current mode active pixel sensor (APS) is presented. Focal plane image processing in the current domain includes a correlated double sampling (CDS) unit for fixed pattern noise (FPN) suppression. The CDS unit is composed of a first generation current conveyer circuit and a class AB cascaded current memory cell. A measured FPN of 0.9% from saturation level is achieved with the CDS unit compared to 1.9% FPN from current mode images without noise suppression circuitry. A 40 by 40 imaging array was fabricated in a standard 0.5 μm process and its functionality was successfully tested. Theoretical analysis for second order non-linear effects is also presented.