On-chip compensation of dark current in infrared focal plane arrays

Abstract

A readout technique for infrared (IR) focal plane arrays (FPAs), involving on-chip compensation of leakage current is presented. This technique employs a tuneable compensation circuit, controlled by a voltage-to-current converter to eliminate the bulk of the leakage current prior to the integration of the weak photo signal at pixel level. To further improve the performance, a correlated double sampling (CDS) circuit is incorporated at the column level to eliminate the fixed pattern noise (FPN) inherent in large sensor arrays with multiple readout lines. A 32×29 element FPA with CMOS sensors was fabricated using 0.8-μm CMOS technology for testing the concept. To mimic the large leakage associated with IR detectors, the testing was carried out under an external light illumination. The results show good compensation of the current caused by the external light and this indicates the effectiveness of the scheme.