Integrated receivers associating an amplifier with a photodiode are studied. The field effect transistor used for the amplifier has been designed and characterized. The FET transistor has been fabricated on a GaAs semi-insulating substrate using Liquid Phase Epitaxy. The structure consists of two epitaxial layers, i.e. one N-GaAs layer for the channel and a P-GaAlAs layer for the gate. The design, technological process and current-voltage characteristics are described. Transconductance values over 10 mA/V have been achieved and the transistor have shown a threshold voltage of - 4.6 V. Integrated receivers whose field effect transistor is associated with a photodiode, enhance the detector sensitivity. The results measured on the field effect transistor will be applied to the amplifier integrating the photodiode