The note introduces the concept of noise in operational amplifier circuits, describing how noise can originate from the amplifier itself, surrounding components, and external sources. It provides practical tools for understanding, characterizing, and reducing noise in high‑accuracy designs.
Key topics include basic voltage and current noise models, noise gain versus signal gain, methods for combining noise sources, and detailed discussion of interference versus inherent noise. The document also covers common random noise types such as Johnson, Schottky, flicker, and popcorn noise, and presents techniques for noise density analysis and filter‑skirt error correction.
| Typical external source magnitude for 60 Hz power | 100 pA |
|---|---|
| Typical external source magnitude for 120 Hz supply ripple | 34 (unit unspecified) |
It is the ratio of the voltage‑noise source to the current‑noise source (eₙ / iₙ) and equals the parallel combination of the source resistances when the two noise contributions are equal.