Thermal noise, also known as Johnson–Nyquist noise, is a fundamental type of electrical noise generated by the random motion of electrons in a conductor, especially in resistors, due to thermal agitation.
Key Concepts:
- Origin: At any temperature above absolute zero, electrons in a conductor move randomly. These motions create fluctuating voltages even without an applied current.
- Universality: This noise exists in all resistive components and is independent of applied voltage or current.
- Temperature Dependent: The intensity of thermal noise increases with temperature—hotter materials exhibit more noise.
- White Noise: Thermal noise has a flat frequency spectrum, meaning it affects all frequencies equally within a certain range.
Importance:
- It sets a fundamental limit to the minimum signal that can be detected or amplified.
- Engineers must account for thermal noise in sensitive electronic systems, such as radio receivers, amplifiers, and digital communication circuits.
Thermal noise highlights the unavoidable role of temperature and statistical fluctuations in physical systems.