Low noise fast bipolar transistors for detector preamplifiers

Abstract
The noise parameters of several species of microwave bipolar transistors were measured using a common base amplifier. The base spread resistance rbb of the transistors was determined from the measured noise parameters. Some species were found to have rbb of less than 30 Ω. For low-noise preamplifier applications in high-energy physics, the series noise contribution from these values of rbb is negligibly small compared with that due to the emitter resistance. Using 2SC3585 as the input transistor, an input noise voltage of 0.98 nV/√Hz and input noise current of 1.81 pA/√Hz were obtained. A simple relation between the structure of the transistors and their r bb was found

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