Analysis and Description of a High Stability Nuclear Pulse Amplifier

A solid state nuclear pulse amplifier designed with emphasis on temperature stability and linearity is discussed. Other characteristics include fast recovery from 500X overload, high count rate capabilities, common mode rejection, low zero-crossover walk, and a choice of pulse shaping (lumped delay lines and RC time constants). The basic amplifier, without shaping, is stable to within 50 ppm/°C at gains up to 1024, and exhibits ±0. 01% linearity up to 10 volts output. The basic feedback loop used in this amplifier has been analyzed in a previous article for gain stability as a function of temperature. The results of this analysis are summarized here, and a theoretical study is made of some additional feedback loop characteristics ¿ frequency stability, transient response, and temperature stability versus input pulse rise time. With large output swings and/or high count rates special problems arise affecting risetime, fall time, linearity, and zero-crossover walk. The causes of these problems are determined using simple feedback loop theory. Finally a diagram of the complete amplifier circuit, with a description of shaping networks, is presented.