DESIGN OF PIXEL LEVEL CMOS READOUT CIRCUITRY FOR CONTINOUS BIAS UNCOOLED BOLOMETRIC LONG WAVE INFRARED FOCAL PLANE ARRAYS

Abstract

Modern IC foundries do not provide large analog storage capacitors. This limits the charge storage capacity for modern uncooled long wave infrared readout circuits. A long integration time in the pixel helps to extend the effective charge storage capacity, reduces the temporal noise, and subsequently reduces the noise bandwidth of the pixel. Modern infrared readout arrays that employ current skimming, a technique which extends the integration time, usually do so at the end of a row or column in the readout array. This thesis research describes an advanced concept of a per-pixel skimming readout approach by incorporating the skimming function inside the pixel. DC pedestal removal techniques such as current skimming allow the pixels to integrate longer by subtracting the DC bias signal. However, a low output conductance current sink is needed to subtract the DC pedestal. This thesis explores the use of cascode circuitry to decrease output conductance. Current skimming alternatives for increasing the integration time in the pixel while maintaining a low output conductance sink for continuously biased uncooled long wave infrared arrays are presented.