Sources of Noise

The noise output Onoise is a combination of thermal, shot, and flicker noise.

• Thermal noise is a variation in current due to random thermal motion of the electrons in physical resistors and bulk materials. Thermal noise is directly proportional to the absolute temperature.
• Shot noise is a fluctuation in the current across P-N junctions in diodes and transistors due to random barrier crossings by electrons and holes in the vicinity of the junction. Shot noise is associated with a direct current flow.
• Flicker noise is a random variation in current associated with contamination and crystal defects in semiconductors. Like shot noise, flicker noise is associated with a flow of direct current. Flicker noise generates a noise signal with energy concentrated at low frequencies; because of this 1/f frequency dependence, flicker noise is also called 1/f noise.