Experimental Validation of Charge-Sensitive Amplifier Configuration that Compensates for Detector Capacitance

This paper presents measurement results of a method by which the shapes of the output signals derived from a front-end readout circuit can be made insensitive to the input detector capacitance, to a degree limited only by the accuracy with which one can make an amplifier with unity gain. A charge sensitive amplifier including the detector capacitance compensation technique was implemented in a standard 180-nm CMOS technology with a 3.3-V supply voltage. The results show that the technique can successfully mitigate the performance degradation that accompanies large detector capacitance derived from either large-area radiation sensors and/or high permittivity materials, such as nanocrystalline assemblies. In order to verify the feasibility of the technique, we measured alpha particle spectra on two different sized silicon detectors that have detector capacitances of 1.26 pF and 21.84 pF, derived from 2-mm- and 10-mm-diameter devices, respectively. A configuration for integrating the fabricated preamplifier with a detector is also described to exploit the technique for any other application or experiment.