Development of Monolithic Microwave Integrated Amplifiers as Readout for Detectors at 4.2 K

Readout amplifiers with high bandwidth and extremely low power dissipation at liquid helium temperature for various superconducting detectors (e.g. SNSPD, HEB and MKID) are necessary to increase the small detector output signals. Different types of cryogenic amplifiers were developed for these applications. The required combination of low noise, large bandwidth, high voltage gain and low power consumption is a driving force for an on-going process of improvements. In this paper, the developments of cryogenic low power hybrid amplifiers, which are based on commercial p-HEMT transistors, will be reported and discussed. In addition, simulation and measurement results of the first developed monolithic microwave integrated circuit (MMIC) amplifier for low power operation will be presented. The MMICs are based on a metamorphic HEMT technology and are realized on a 3×1.5 mm² area. First measurements at room temperature showed a bandwidth of 0.3 GHz up to 9 GHz with a gain of 23 dB at 90 mW and 1.3 GHz up to 8 GHz with 20 dB of gain at 42 mW, respectively. The power consumption could be reduced by cooling the devices down to 7.2 K. At almost identical bandwidths, the measured gain decreased to 10 dB at 22 mW and 15 dB at 9.5 mW.