MONOLITHIC GAAS CURRENT-SENSITIVE CRYOGENIC PREAMPLIFIER FOR CALORIMETRY APPLICATIONS

We have realized low-noise monolithic GaAs preamplifiers using ion-imp lanted technology, to operate under low temperature and high radiation field conditions. The evaluation of noise, amplitude and timing distr ibutions of a batch taken after first mass-production run is presented . The current-sensitive preamplifier is linear up to 8 mA of input cur rent and able to cope a 2.2 nF detector capacitance, showing fast resp onse (GBW product similar to 1.7GHz) and very low series noise. Very g ood noise performance at LAr temperature is obtained by using large ar ea MESFET (l.w = 3.24000 mu m(2)) as a head transistor, which exhibits at 8mA standing current and only 10mW power dissipation, intrinsic ga in mu = g(m).r(ds) = 15 and noise referred to the input 0.30 divided b y 0.35 nV/root Hz. According to our estimation, second stage noise con tribution is negligible. Radiation damage from neutrons and gamma-irra diations as well as protection network against HV discharges are discu ssed.