Measurements of junction-transistor noise in the frequency range 7-50 kc/s

The paper describes an investigation to determine the variation of junction transistor noise with operating conditions (frequency, temperature, voltage and current) in the frequency range 7-50 kc/s. A detailed investigation involves a statistical analysis of a very large number of measurements, but since in this case it was required to determine only approximate laws, a small number of measurements were taken with the assumption of a large possible error. The noise voltages were measured using the superheterodyne principle to give constant bandwidth over the frequency range. The analysis of the results is made using the principle of two equivalent noise generators in the input circuit: theoretical considerations link these with the minimum noise factor and optimum source resistance, which together determine the noise characteristics of the transistor.