Low power BiCMOS ASIC for wide energy range X- gamma-ray imaging and spectroscopic detectors

A low-power, low noise Application Specific Integrated Circuit (ASIC), designed to read out CdTe array detectors for X–γ ray imaging and spectroscopy on satellite or balloon telescopes, is presented. The chip ELBA has been realized in 0.8 µm BiCMOS technology; the front-end includes preamplifier, shaper, peak stretcher, discriminator with a dynamic range from 20 keV to 2 MeV of photon energy. The reset of the preamplifier and the high time constant of the shaper are obtained with a very compact current conveyor feedback. A multichannel prototype has been realized with a digital back-end including multiplexer, decoder, double pulse detect and logic circuitry for chip testing and calibration. The measured noise level is in between 150 and 500 electrons r.m.s. corresponding to 1.5–5 keV FWHM in CdTe detectors. The total non-linearity is below 71.5% and the cross-talk between two neighboring channels is about 0.7%. The circuit is powered with a single supply at +4V with a total power consumption of 1 mW/channel.