High-order microsecond-range current-feedback filtering cell for high resolution spectroscopy in BiCMOS technology

The subject of this work is a novel current mode approach to design monolithic spectroscopy amplifiers virtually of any order. The proposed topology is suitable to design spectroscopy amplifier with a wide range of time constants (/spl sim/0.1-10 /spl mu/s) in a very compact scheme. We have designed in 0.8 /spl mu/m BiCMOS technology two 4th order shaping amplifiers (500 ns and 167 ns shaping times) to be coupled to monolithic arrays of silicon drift detectors for high resolution X-ray spectroscopy. In this paper we present the main issues of the circuit design and a detailed discussion of the results of the experimental characterization. The measured integral-non-linearity is below /spl plusmn/0.1% and the achieved energy resolution at the Mn K/spl alpha/ line (measured with the proposed spectroscopy amplifier coupled to a 5 mm/sup 2/ Peltier-cooled SDD) is 160 eV FWHM with 500 ns shaping time, comparable to the one obtained with a commercial shaping amplifier with the same time constant.