An analytical model of preamplifier noise identification in a spectrometric system

An analytical model of preamplifier noise identification in a spectrometric system is presented in the article. It allows analysis of normal passive pulse shapers, general time-invariant systems as well as time-variant systems. An equivalent noise charge (ENC) is modeled as the sum of three components: (i) proportional to the amplifier shaping time, (ii) inversely proportional, and (iii) independent of the amplifier shaping time. The Least Squares Method for identifying the noise components of the spectrometric system was used; measured values of ENC were fitted to the theoretical dependence on peaking time τ0. Analytical formulas have been derived for the values of coefficients included in the dependence of ENC on the shaping time for CR−(RC)n shaping for any value of n. The conclusion of this analysis may be used for the optimization of spectrometric systems.