Cryogenic ultra-low noise HEMT amplifiers board

High Electron Mobility Transistors (HEMTs), optimized by CNRS/LPN laboratory for ultra-low noise at a very low temperature, have demonstrated their capacity to be used in place of Si JFETs, when very high input impedance and working temperatures below 100K are required. We have developed and tested simple amplifiers based only on this transistor technology, in order to work at a temperature as low as 1K or less. They demonstrate at 4.2K a typical noise of 1.6nV/Hz at 100Hz, 0.42nV/Hz at 1kHz and 0.32nV/Hz at 10kHz, with a gain of 50 and a power consumption of 1.4mW per channel. Two boards have been designed for two different research applications: one for the readout of GMR magnetometers for medical and space applications, the other for search of weakly interacting massive particles (WIMPs) in Edelweiss experiment (HARD project).