Analog Circuit Design Volume Three

Chapter 457

Operational amplifier selection guide for optimum noise performance

George Erdi

Abstract

A guide to selecting operational amplifiers for optimum noise performance is given.

Keywords

Operational amplifier

noise

The LT1028 is the lowest noise op amp available today. Its voltage noise is less than that of a 50Ω resistor. In other words, if the LT1028 is operated with source resistors in excess of 50Ω, resistor noise will dominate. If the application requires large source resistors, the LT1028’s relatively high current noise will limit performance, and other op amps will provide lower overall noise.

In general, the total noise of any op amp (referred to the input) is given by:

$\begin{array}{c}\text{total noise}=\hfill \\ \sqrt{{\left(\text{voltage noise}\right)}^2+{\left(\text{resistor noise}\right)}^2+{\left(\text{current ...}\right)}^{}}\hfill \end{array}$