High temperature electronics using silicon technology

In this paper, techniques used to realize precision CMOS circuits for use in down-hole oil and gas field applications are described. The focus is on bulk CMOS circuits so that complete mixed analog/digital precision monolithic data acquisition systems can be fabricated in a standard 5 V digital process. Successful designs to date include an A/D converter with 15 b absolute accuracy at 175/spl deg/C in 3 /spl mu/m CMOS, an autozeroed op amp with low-offset voltage and current at 200/spl deg/C in 1.2 /spl mu/m CMOS, and a high-resolution A/D system for resistance bridge transducers incorporating input offset voltage and bias current error suppression in 1.2 /spl mu/m CMOS.