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