(A) study on performance improvement of low noise readout circuit for infrared detector array

Abstract

In this dissertation, the performance enhancement of Silicon CMOS readout circuit for infrared focal plane arrays has been studied. The readout circuit converts photocurrent induced in infrared detector array into raw video signal and recently, it has often limited the performance of IRFPA. For the improvements of the low noise readout circuit, a noise bandwidth suppression circuit and a smart TDI readout circuit are suggested in this study. Noise property is the prime consideration in designing readout circuit. As results of noise analysis, it was noted that the output stage was a dominant noise source in readout circuit and its noise should be reduced. Thus, the noise bandwidth suppression (NBS) circuit is proposed and it can reduce output stage noise effectively. From experimental results, it was found that the NBS circuit reduced the output stage noise from 267 $\mu V$ to 168 $\mu V$ at 300 K. Using the NBS circuit, it is expected that the output stage noise will be about 86 $\mu V$ at the operation temperature of 77K and the readout circuit can satisfy near 95% BLIP condition. TDI (time delay and integration) configuration is a method to effectively increase the integration time that an element is looking at a specific point in a scene. However, the integration capacitor in TDI should be larger because of the increased integration time, and thus it occupies almost whole area of a unit cell. Besides, TDI increased the number of dead pixels. Thus, in order to settle these problems, we proposed a smart TDI readout circuit performing background suppression, non-uniformity compensation, and dead pixel correction. In the proposed readout circuit, the integration capacitor size was reduced to 1/5 and trans-impedance gain increased by five times. The skimming current error was measured to less than 1.25 nA and the non-uniformity was reduced to 1.02 nA. Moreover, the dead pixel correction is expected to largely improve production yield and operability of IR dete...