This book is an introduction to the physics of electronic noise and fluctuation phenomena in solids. It is written for physicists and electrical engineers interested in investigation of electric and magnetic noise and in development of sensitive solid-state devices. It can be used also in graduate schools of the Departments of Physics and Electrical Engineering.

Fluctuations or noise are spontaneous random (stochastic) variations of physical quantities in time or, more precisely, random deviations of these quantities from some mean values that are either constant or vary nonrandomly in time. Fluctuations are a manifestation of the thermal motion of matter and discreteness of its structure. The introduction of the concept of fluctuations and development of the physics of fluctuations is one of the greatest achievments of twentieth-century physics. The theory of Brownian motion developed by A. Einstein and by M. von Smoluchowski in the first decade of this century and its experimental proof by J.B. Perrin and T. Svedberg was a strong and, perhaps, the final argument in favor of the molecular-kinetic concept of heat. Hence, the physics of fluctuations is of great conceptual importance.

The applications of the physics of fluctuations stem from the fact that the ultimate accuracy of measurement of any physical quantity is limited just by fluctuations of this quantity, and the ultimate sensitivity of many devices is also limited by fluctuations.