When designing a measurement signal chain, it is important to work through a noise analysis to determine if the signal chain solution will have low enough noise so that the smallest signal of interest can easily be extracted.

This paper presents the steps needed to carry out a theoretical analysis on the noise performance for a high speed wide bandwidth signal chain. Although a specific signal chain is chosen for the analysis, the steps highlighted can be considered valid for any type of signal chain. Five main phases are suggested:

  • Declaring the assumptions
  • Drawing a simplified schematic of the chain signal
  • Calculating the equivalent noise bandwidth for each of the signal chain blocks
  • Calculating the noise contribution at the output of the signal chain for all blocks
  • Adding all noise contributions

The analysis shows how simple math can be used to describe all noise contributions. Gaining an understanding of how each block contributes to the overall noise allows the designer to appropriately modify the design (for example, choice of components) to optimize its noise performance.