Abstract: A charge integration-type preamplifier for use with a radiation detector. The preamplifier is capable of electronically resetting a feedback capacitor, prevents intrusion of noise, and offers high resolution and high counting rate. An inverting amplifier is connected with the radiation detector and has an N-channel FET at its first stage. The output signal from this amplifier is fed back to the gate of the FET via an electrostatic capacitor. The preamplifier further includes a reset means which urges the voltage at the output of the inverting amplifier to rise via the capacitor by utilizing the feedback action. The junction between the gate and the source of the FET is forward-biased to release the charge stored in the capacitor to the source, thus resetting the capacitor. This maintains continuous operation. Thus, any interference causing noise between the radiation detector and the gate of the FET is not created. Furthermore, the disturbance caused by the resetting can be removed in a short time.

Abstract: A pulse shaping circuit for use in a radiation detector. This circuit is adapted for x-ray spectroscopy. The pulse shaping circuit comprises a circuit for converting the output signal from the radiation detector into a step-function waveform, a pseudo-Gaussian filter consisting of a plurality of cascaded filter circuits, an adder circuit, and a gated integrator for integrating the output from the adder circuit. The adder circuit proportionally adds the outputs of each of the plurality of filter circuits in a predetermined manner and sums them up. The pulse shaping circuit achieves a high counting rate and a high resolution.