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 (∼0.1-10 μs) in a very compact scheme. We have designed in 0.8 μm 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 ±0.1% and the achieved energy resolution at the Mn Kα line (measured with the proposed spectroscopy amplifier coupled to a 5 mm² 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.