We present 2 versions of a 2-stage all-Nb dc SQUID amplifier with different designs of the first SQUID loop. The amplifiers have large (3 μH and 4.8 μH) input inductances matched with the inductances of the first stage SQUIDs by 2 transformers. Effective coupling factors k~2 (0.04 and 0.17) and intrinsic energy resolutions (22 h and 80 ft) have been measured. An advanced fully integrated version of the SQUID amplifier is also discussed.
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