Design of a resistorless ASIC preamplifier for HPGe detectors with non-linear pole/zero cancellation and controlled fast-reset feature

An original low-noise ASIC preamplifier is under development for high-resolution gamma-ray spectroscopy with germanium or other semiconductor detectors. The preamplifier is being designed in a 0.35 J.lm 5V CMOS technology, uses no feedback resistor and incorporates original techniques to optimize its performance. The first novelty consists of a nonstandard circuit structure for non-linear pole-zero compensation, aimed at removing the non-linear behaviour of the continuous non-resistive charge reset mechanism. The second consists of a controlled fast-reset feature aimed at greatly reducing the dead time caused by hits of high-energy charged particles. Such events are typical in nuclear physics experiments employing radioactive ion beams and in fusion-evaporation reactions which yield a prolonged saturation of the system that prevents detection of the subsequent decay events. The peculiar features of this preamplifier could be also exploited in other applications employing semiconductor detectors.