A Low-Noise Low-Input Conductance Preamplifier for Gravitational Research

We report on the specification, the design, and the characterization of a FET-input low-noise preamplifier with low-input conductance that has been developed for gravitational-wave research. At approximately 900 Hz the noise temperature of the preamplifier is 69 mK and its input conductance is ~ -2 nS. This preamplifier has recently been used during the first cooling to liquid helium of a 2.2-ton gravitational-wave antenna equipped with a capacitive resonant transducer.