Hi, I'm a noob when is comes to these kinds of measurements on a spectrum analyzer. Take for example two LDOs: 1. http://www.analog.com/media/en/technical-documentation/data-sheets/ADM7154.pdf 2. http://www.ti.com/lit/ds/symlink/lp5907.pdf (see figure 17) They claim to be ultra low noise LDOs and they measure the noise on the output of the LDO by feeding the output into a spectrum analyzer. My questions are: 1. How does a spectrum analyzer measure Noise Spectral Density. Does the analyzer put a bandpass around a particular frequency and measure the amplitude? How can it do so very well for a signal that is in the signle digit Hertz as well as MHz. 2. Why are the units in V/sqrt(Hz). 3. If I integrate the curve for the noise spectrum density over a particular frequency range do I get the total power of the noise signal? Thanks.