A smart reset circuit for low-noise preamplifiers of X-gamma ray sensor signals

We have developed a mixed continuous-pulsed reset technique suitable for multi-channel X-gamma ray sensor preamplifiers. The continuous-reset mode is used for typical signal amplitudes within the ADC input range, or 1 V. The pulsed-reset mode works on larger signal amplitudes, either caused by individual events or by bursts of piled-up events. Such operation mode maximizes the live time in the typical energy range and minimizes the dead time caused by ADC saturation on large individual signals or at high count rates. The amplitude of large individual signals can also be estimated from the reset time still achieving a high resolution. Using this technique and a bulky High Purity Germanium detector we got a "continuous-reset" range of 2 MeV with a resolution of 2.02 keV fwhm at 1.408 MeV, and an extended "pulsed-reset" range of 27 MeV, with a typical resolution of 0.3% at 27 MeV.