Low noise integrated CMOS front-end electronics for gamma rays spectroscopy

We present a new integrated CMOS front-end electronics for gamma rays spectroscopy designed to cope with HPGe detectors with or without segmentation. It consists of two key elements: i) a low noise preamplifier with integrated input transistors and fully differential interior circuit topology, connected to ii) a fully differential operational amplifier with complete rail to rail output signals capability for light differential loads, limited to 500 mV from the rails levels for 200 Ohm differential load. Among the key feature of the front-end electronics are: i) lower power consumption (< 50 mW) and much smaller dimensions per channel compared to equivalent hybrid preamplifiers; ii) possibility of direct connection also to low impedance long differential cables, thanks to the integrated differential output driver; iii) possibility of in-line tuning of the fundamental bias currents of both preamplifier and differential line driver, which allows either to lightly adjust the front shape of the output signals or even to compensate for much larger bias current changes induced by deep temperature shifts; iv) possibility of operating at any temperature level, from room temperature down to cryogenic temperatures (77 K), with almost the same performances in terms of signal front rise/fall time and usually slightly lower input equivalent charge noise at low temperatures. The front-end electronics has been designed in the AMS HV CMOS 0.8 um CXZ technology.