A robust SOI gain-boosted operational amplifier targeting high temperature precision applications up to 300°C

Data acquisition and signal processing at elevated temperatures are facing various problems due to a wide temperature range operation, affecting the accuracy of the circuits' references and elementary building blocks. As the most commonly used analog building block, the operational amplifier (op-amp) with its varoious limitations has to be enhanced for wide temperature range operations. Thereby major effort is put into maximizing signal gain and simultaneously reaching high gain-bandwidth also for high temperatures. Future robust design approaches have to consider a growing operating temperature range and increasing device parameter mismatch due to the downsizing of integrated circuits. Addressing one of the major problems in circuit design for the next decades, compensating the effects through new design approaches will have a lasting impact on circuit design. In this paper we present a high gain operational amplifier with a folded-cascode and gain-boosted input stage, fabricated in a 1.0 µm SOI CMOS process. The operational amplifier was designed for an operating temperature range of -40...300°C. Major effort was put into a robust design approach with reduced sensitivity to temperature variations, targeting high precision applications in a high temperature environment. With a supply voltage of 5 V, the maximum simulated current consumption of the op-amp is 210 µA which leads to overall maximum power consumption of 1.05 mW. The open loop DC gain of the amplifier is expected to reach a minimum of 108 dB and a unity-gain-frequency of 1.02 MHz at a temperature of 300°C. For all temperatures the phase margin varies from 55...70 degrees for a 3 pF load.