Investigation of Static and Dynamic Behavior of Off-the-Shelf Operational Amplifiers at Cryogenic Temperatures

In modern particle physics experiments, various electronic devices are frequently required to operate within noble liquids at cryogenic temperatures. Within the framework of the deep underground neutrino experiment (DUNE), a need has arisen to develop a dc-dc boost converter with an analog feedback loop control composed of discrete components, all capable of functioning at cryogenic temperatures. Consequently, operational amplifiers (OpAmps) must also be adapted to meet these requirements. However, there is no existing literature on off-the-shelf OpAmps with the required characteristics for cryogenic temperatures, and on circuit-ready measurement setups applicable for obtaining these characteristics for the selected OpAmps. For this reason, this article explores a measurement setup solution for cryogenic temperatures and the characterization of two OpAmps suitable for the analog control scheme. Due to application requirements, the quiescent current, offset voltage, offset input current, bias input current, open-loop voltage gain, and gain at 10 or 100 kHz have been measured in function of the temperature, from 123 to 333 K, and directly inside a liquid nitrogen (LN2) detector. Furthermore, this work required studying the thermocouple effect introduced at the interface between LN2 and air, which must be considered for the calculation of the desired OpAmp characteristic values. Finally, the measurement uncertainty has been evaluated and presented in this article.