Improved Dynamic Range Charge-Sensitive Amplifier

Charge sensitive amplifiers (CSA) are key elements for the readout of charge signals produced by ionizing radiation and particle detectors. In nuclear microelectronics, these circuits are characterized by stringent requirements in terms of equivalent noise charge (ENC), and maximum input charge specification, which is tied to the voltage output swing capability of the amplifier itself. The need for periodic or continuous discharge of the feedback capacitance further constrains the design choices. In this work, a circuital solution that acts on the feedback discharge path to optimize the quiescent operating point of the CSA is presented, allowing an increase in the effective dynamic range of the CSA without affecting the spectroscopic resolution of the system. In addition, the proposed reset architecture allows to use a single power supply, avoiding the double supply generally used to increase the dynamic range, gaining in system compactness. Experimental measurements show an increase of + 107% in the dynamic range with respect to standard reset architectures of state-of-the-art CSAs for low-capacitance (≤ 0.1 pF) semiconductor radiation detectors, achieving a total maximum input charge of ' 3 × 105 el. (47 fC), corresponding to 1.08 MeV equivalent energy in silicon or 1.31 MeV in cadmium-zinc-telluride detectors. The preamplifier implements a fast feedback capacitance discharge rate of 2.5 fC/ns (t 90fall−10 = 18.8 ns over the full output range), and preserves an excellent intrinsic noise performance of 3.7 electrons rms, making it suitable for high-speed, high-energy-resolution spectroscopy applications.