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Chapter 2: Introduction to Op-Amp Noise - Pg. 13

CHAPTER 2 Introduction to Op-Amp Noise 2.1 Op-Amp Noise Analysis Technique The goal of op-amp noise analysis technique is to calculate the peak-to-peak output noise of an op-amp circuit based on op-amp data sheet information. As the technique is explained, we will use formulas that apply to most simple op-amp circuits. For more complex circuits, the formulas can help to get a rough idea of the expected noise output. It is possible to develop more accurate formulas for these complex circuits; however, the math would be overly complex. For the complex circuits, it is probably best to use a three-step approach. First, get a rough estimate using the formulas; second, get a more accurate estimate using Spice; and finally, verify your results through measurements. As the example circuit, we will use a simple noninverting amplifier with a Texas Instruments OPA277 (see Figure 2.1). Our goal is to determine the peak-to-peak output noise. To do this, we have to consider the op-amp current noise, the op-amp voltage noise, and the resistor thermal noise. We will determine the value of these noise sources using