Making accurate voltage- and current-noise measurements on op amps in the nanovolt and femtoamp range can be challenging. One excellent approach consists of designing a test platform with an effective background noise at least 10 dB lower than the device under test (DUT). To obtain a test platform with this level of performance requires:

• the removal of environmental electrical disturbances;
• the use of batteries for low noise voltage sources;
• the use of a Post Amplifier (PA) to raise the DUT noise above the measurement system's noise floor;
• control software to automate collection of data and processing software to eliminate external noise and generate the DUT's voltage (en ) and current (in ) noise plots.

The result is a test platform that is capable of measuring nanovolts and femtoamps down to 0.1 Hz.

The author, Don LaFontaine, is a Senior Principal Application Engineer with Intersil's Analog/Mixed Signal product line, with a focus is on precision analog products.

This article is presented in two parts:
Part 1: click here
Part 2: will be posted on April 30, 2009