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 100 K 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 1 K or less. They demonstrate at 4.2 K a typical noise of 1.6 nV/Hz at 100 Hz, 0.42 nV/Hz at 1 kHz and 0.32 nV/Hz at 10 kHz, with a gain of 50 and a power consumption of 1.4 mW 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).