The main types of noise in electronic devices (in particular, in the input stages of linear amplifiers, generators, etc.) are considered. Achieving a low noise level in these devices is one of the determining factors for obtaining good amplitude and time resolution in spectrometry of ionizing radiation and one of the most important problems of radio electronics. The book is intended for physicists and engineers developing or operating sensitive radio equipment. It can be useful for teachers, graduate students and students of radio engineering and engineering and physics specialties.