Charge sensitive preamplifiers using GaAs MESFETs have been designed to satisfy requirements of high dynamic range, low power dissipation and low noise at short shaping times. They use SGM20006M MESFETS, a replacement type for the 3SK164. The main parameters of the preamplifiers with a detector capacitance of 400pF are the following ones: the equivalent noise charge (ENC) is 5500 rms electrons at 77K at 100-mu-s gaussian shaping time; the input resistance 22-OMEGA, the power dissipation 52 mW with 0.2% integral nonlinearity and 2 V output. Radiation damage test have been performed showing a fairly high ENC insensitivity to 10(14)n/cm2 neutron fluence particularly at short shaping time. Ionizing radiation increases the ENC by a factor 2 when the dose is 10 MRad(Si).