A Wideband Cryogenic Amplifier for SNSPD Read-Out System

A wideband cryogenic amplifier used for SNSPD redou-out system is designed in this paper. Packaged SiGe HBT BFU725F/N1 which could be operated in 4K temperature is utilized as the key component of this amplifier. The simulation results show that the noise figure is less than 1 dB over 100kHz to 1 GHz frequency range, the gain is about 20 dB and the gain flatness is less than 1 dB, the reflection coefficients are less than −10 dB. This wideband cryogenic amplifier could be integrated directly with SNSPD to improve the performance of SNSPD read-out system.