Very-low-noise multiplexing with SQUIDs and SiGe HBTs for readout of large superconducting bolometer arrays

We present an ultra-low-noise instrumentation based on a standard BiCMOS SiGe 0.35 μm ASIC operating at cryogenic temperatures. The main functions of the electronic circuit are the readout and the multiplexing of SQUIDs/TES arrays. We report the cryogenic operation of the ASIC dedicated to the readout of a 2×4 pixel demonstrator array. We particularly emphasise on the development, and the test phases of an ultra-low-noise (0.2 nV/√Hz) cryogenic amplifier designed with two multiplexed input. The cryogenic SiGe amplifier coupled to a SQUID in a FLL operating at 4.2 K is also presented.