Abstract: A method for detecting intrinsic radioactivity of radioactive samples includes: providing a sample of material to be subjected to a measurement of emission of X photons from radioactive samples, the sample being stratiform and having two main sides; placing one or more semiconductor-type or bolometer-type detectors near one or two of the two main sides of the sample, the detectors having a surface covering the whole or most of the area of the main sides; measuring the emission of X photons, respectively in the presence and in the absence of the sample, for a predetermined time interval; determining the energetic spectrum of the emission of X photons, respectively in the presence and in the absence of the sample, by measuring the number of counts produced by the emission; subtracting the measurement of the number of counts in the absence of the sample from the measurement of the number of counts in the presence of the sample, thus obtaining a useful measurement of the number of counts; estimating the X-ray det

Abstract: The amplifier comprises a first field effect transistor controlled by the input signal of the amplifier and a current generator for the supply of said first transistor. The latter is biased so as to operate in its linear region and in cascade with it there is provided at least one second field effect transistor biased in a similar way, suitable for raising the output impedance of the amplifier, and thus its gain, to a value corresponding to the desired use.