Reduction of ENC in presence of a series inductor, an ideal transformer and a finite-width filter

This paper studies the benefits on the signal-to-noise ratio obtained with the introduction of a transformer with a series inductor introduced between a capacitive detector and the first stage of the shaping amplifier, in presence of time constraints on the output of the amplifier. The optimum weighting functions and the concerning values of the Equivalent Noise Charge are investigated. The paper demonstrates that, with suitable transformer ratios, the value of the ENC ² can be reduced by a factor 1.9 with respect to the case of capacitive matching without inductor.