Cryogenic transimpedance amplifier based on a commercial operational amplifier

A transimpedance amplifier working at a temperature around 50 K has been developed. The design of the amplifier is targeted to use specifically in dry dilution refrigerators for measuring quantum devices. Electrical characteristics such as input noise, bandwidth, and gain of several commercial operational amplifiers (op amps) operating at 77 K were evaluated. From a screening process, the op amp OPA827 was chosen for the benchmarking of a cryogenic transimpedance amplifier. The conductance of a quantum point contact (QPC) at 100 mK was measured in a dry dilution refrigerator in order to compare the cryogenic and room temperature performance of transimpedance amplifiers built using OPA827. The results were analyzed with a noise model describing the measurement system. We found that it is more advantageous to use a cryogenic transimpedance amplifier when the impedance of the device under test is high as in the case for most quantum devices.