The future high-energy physics experiments, based on the new high-luminosity accelerators, will require a new generation of front-end monolithic electronics characterized, in particular, by high speed and low-power dissipation. In this perspective, the performances of Si and GaAs field effect transistors (FET's) are compared here in conditions of low-power dissipation. The advantages of solutions based on GaAs FET's, in applications requiring fast shaping times, are presented and experimental results are reported. The criteria for the optimum choice of the input transistor dimension and of its bias point are discussed.