XPS: a multi-channel preamplifier-shaper IC for X-ray spectroscopy

An integrated circuit featuring 48 channels of charge-sensitive preamplifiers followed by variable-gain pulse shaping amplifiers is being developed as part of an X-ray spectrometer with a highly segmented detector to handle high fluxes in synchrotron experiments. Such detector systems can provide excellent energy resolution combined with one-dimensional spatial information. The IC provides preamplifier and shaping amplifier functions and its output stage is capable of driving conventional ADC modules directly. Reported here are first measurements made on the performance of a 16-channel prototype integrated circuit. At present, the preamplifier-shaper circuit achieves an equivalent input noise of 26 electrons rms at 2 μs peaking time with a 0.2 pF external capacitor, which is similar to the capacitance of a single detector element. Pulse shaping is accomplished by a novel CR-RC² filter section that utilizes several high-linearity transconductor circuits to provide a broad range of continuously variable peaking times while still maintaining the linearity and noise performance necessary for X-ray spectroscopy. The design was fabricated in standard 1.2 μm CMOS technology