Spectroscopy charge amplifier for detectors with integrated front-end FET

A charge amplifier, especially designed for FET integrated on silicon radiation detectors, is presented. The circuit is based on the forward biased FET amplifier configuration, which does not require the feedback resistor nor additional devices for resetting. The severe constraints on the preamplifier design, imposed by the low transconductance of small size integrated FET's, are analyzed as far as loop-gain, bandwidth, and noise are concerned. A circuit topology which satisfies all the requirements even at relatively fast shaping time (1 /spl mu/s) is proposed and experimentally tested.>