Minimizing system noise in low power, cost conscious designs is critical. To attain the lowest noise floor and best performance from signal conditioning circuitry, designers must understand component level noise sources and account for them when calculating the overall noise of  an analog front end—it is critical to read and understand beyond the limited data sheet noise specs in order to achieve high resolution with very small signals. Every sensor has its own noise, impedance, and response  characteristics, so matching these to the analog front end is an important part of the design process. There are a number of ways to calculate the noise of a circuit—all of these should start with configuring the signal conditioning circuitry optimally before conducting the noise analysis and calculation. If there is a good SPICE model available for the op amp, using SPICE is the easiest approach.