A low noise amplifier includes a cascode device which includes at least a first and a second transistor having a terminal in common. The output terminal of the second transistor is the output terminal of the cascode device and is coupled to the output terminal of the amplifier. The amplifier includes a first circuit means suitable for the polarization of the second transistor. The first circuit means is positioned between a supply voltage and another terminal of the second transistor. The amplifier includes a second circuit means connected to the output terminal of the cascode device and is operative at a given frequency (.omega.). The first circuit means includes a first series of a resistance and a capacitance and the second means has a second series of a resistance and a capacitance. The first series is coupled between the other terminal of the second transistor and ground and the second series is coupled between the output terminal of the cascode device and ground. The values of the resistances of the first and of the second series are much lower than the module values of the respective capacitive impedances of said first and of said second series at said given frequency (.omega.).