High-resolution VLSI spectroscopy amplifiers based on a current-mode scheme

A novel current mode approach to design monolithic spectroscopy amplifiers virtually of any order is proposed. The proposed topology is suitable to design spectroscopy amplifiers with high-value (∼1-10 μs) time constants avoiding excessive area wastage. We have designed in 0.8 μm BiCMOS technology a 5^th order shaping amplifier (0.5 μs shaping time) to be coupled to monolithic arrays of Silicon Drift Detectors (SDDs) 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 ±0.2% and the achieved energy resolution at the Mn Kα line (measured with the proposed spectroscopy amplifier coupled to a 5 mm² Peltier-cooled Silicon Drift Detector) is 159 eV FWHM fully comparable to the one obtained with a commercial shaping amplifier with the same time constant.