A CMOS analog-digital integrated circuit for charged particle spectrum measurements

We present a first prototype for a CMOS analogdigital integrated circuit suitable for energy spectra measurements of space plasmas, using solid state detectors. Our single chip system includes a charge preamplifier followed by a pulse shaper, an energy discrimination block and an accumulation stage. The particle energy spectrum is measured in 10 channels through a novel non-linear flash A/D converter and is stored in equinumber 11-bit registers, which can then be selectively addressed, read out, and reset. The overall noise performance with detector capacitance of 50 pf is equivalent to ~ 7000 electrons. The power dissipation is ~ 120 mW. The complete system can resolve particle counting rates as high as 1.5 X lo
⁵
counts/sec, and as high as lo6 counts/sec in the pulse height analysisaccumulation mode. The small size and low power dissipation makes such an application attractive for space experiments and portable nuclear instrumentation.