Low noise fast bipolar transistors for detector preamplifiers

The noise parameters of several species of microwave bipolar transistors were measured using a common base amplifier. The base spread resistance r/sub bb'/ of the transistors were determined from the measured noise parameters. Some species were found to have r/sub bb'/ of less than 30Ω. For the low noise preamplifier applications in high energy physics, the series noise contribution from these values of r/sub bb'/ is negligibly small compared with that due to the emitter resistance r/sub e/. A simple relation between the structure of transistors and their r/sub bb'/ was found