Equivalent Noise Charge Contribution of the √f Parallel Noise in Nuclear Spectroscopic Measurements Using Different Shaping Amplifiers

Abstract

In this work both a theoretical study and experimental measurements are shown to describe the ENC (Equivalent Noise Charge) contribution of the parallel √ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> noise of a charge-sensitive pre-amplifier in a nuclear spectroscopic chain. Previous works have demonstrated that this noise is produced by the distributed capacitive coupling to bulk of the preamplifiers’ high-valued feedback resistors, which give rise to a R-C structure known in literature as "diffusive line". The introduced noise is particularly evident when such devices are integrated in a chip using a polysilicon layer that has intrinsically high distributed capacitance to the chip’s bulk. Different shaping amplifiers are taken into consideration (analog quasi-Gaussian, digital trapezoidal/triangular, CR-RC <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>n</i></sup> ) and closed-form expressions of noise coefficients are given whenever possible.