Electronic noise, as opposed to acoustic noise, affects  all electronics, analog and digital alike, however is critically important in some areas of application, such as communications Radio Frequency (RF), amplifier design, Analog to Digital conversion, and in PLL's (phased locked loop circuits), which are subject to phase noise or "Jitter".

Noise is created by the physics of the carrier conduction (e.g. electrons), as the discrete carriers traverse the atomic lattice of the semiconductor material, the dynamics of which are defined by quantum mechanics.
The presence of noise in electronic design, has been well understood by designers for many years, and regarded as a "fundamental" limit.

A tiny signal (a group of electrons in time) in the presence of noise, of a similar magnitude, is hard to detect and recover. Reducing the noise in the amplifier (e.g. Operational Amplifier) determines how small an electronic signal can be detected and processed. Although 'shot' noise was first observed 115 years ago in Vacuum tube amplifiers, and also in the first transistors, the research continued, in an effort to find methods for reducing its presence. These devices are the conclusion of the research work started at the University of Surrey some years ago.
The need to detect very small signals for example in medical imaging, medical implants, fetal heartbeat, or the signal from the Voyager probe many millions of miles from earth, are all examples, of the areas which push back the performance envelope. This allows the next generation of semiconductor products to be developed. 

The JAMES simulator /james-simulator has been used to design devices with Ultra Low noise.