Low-frequency white noise generators for biomedical systems

There is a need for electronic noise sources for investigation of biological and medical research equipment. Such sources need to provide a "white noise" output with a frequency spectrum flat from one to one hundred Hertz. The present paper describes two designs of such sources. The spectra are measured and compared. One course is the reverse-biased junction of a transistor base-emitter junction operating in the avalanche mode. The second source is a MOS IC pseudo-random digital signal. In both cases, the spectra are presented. The choice between the two sources depends upon the application. For most applications, either source is shown to be satisfactory.