Novel high uniformity readout circuit allowing microbolometers to operate with low noise

The capacitive transimpedance amplifier (CTIA) is usually taken as a preamplifier circuit for uncooled microbolometer due to it´s excellent bias control, high injection efficiency, linearity, and noise performance. However, the nonzero input offset voltage in the operational amplifier will cause a significant spatial non-uniformity. In this paper, we have developed a novel CTIA for uncooled microbolometers with correlated double sampling technique. The proposed CTIA suppresses the offset voltage and flicker noise of the op-amp. It improves the readout uniformity and also the temporal noise performance. A 320 × 240 uncooled microbolometer focal plane array based on the proposed circuit was implemented on silicon using a 0.5μm CMOS technology. A thermal IR image is, thus, obtained for F/1 optics and at 60 Hz frame rate. The test spatial fixed pattern noise voltage and temporal root mean square (RMS) noise voltage are 0.0286 V, 546μV, respectively.