A cryogenic ultra-low noise CMOS preamplifier for point-contact HPGe detectors

A cryogenic ultra-low noise CMOS CSA has been developed for point-contact HPGe detector for CDEX dark matter search experiment. Several design techniques have been adopted including adjustable biasing for low temperature operation, fast reset circuits without increasing parallel noise and an output stage with high capacitive drive capability. A prototype chip has been fabricated in 0.35µm CMOS technology. ENC noise was measured to be 6.5 electrons at low temperature. The energy resolution of 0.59% FWHM for Cs-137 662keV full energy peak was measured with a point-contact HPGe detector, compared to 0.2% FWHM using a JFET-input-transistor CSA. Detailed design and test results will be reported in this paper.

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