On the choice of a element low-noise preamplifier on bipolar transistors

The dependence of the preamplifier equivalent noise charge (ENC) on the detector capacitance, shaping time and collector current of the head transistor is presented. The measurement results are in a good agreement with calculations based on a simple noise model, so tedious ENC measurements may be replaced by a simple selection of transistors on distributed base resistance and current gain factor and unsophisticated calculations. Soviet KT382 - type transistors have the same noise performance as the best Japan transistors NE578 and NE021 and it is possible to use it as a head transistor for nuclear electronics applications