The LT1763 familiy is a favorite for audio projects because it has low noise figures. Among linear regulators it is probably universally preferred by audio diy aficionados.
In order to compare other regulators to this benchmark device, I decided to calculate the Vrms noise in each of the fequency ranges provided by the chart. The Vrms noise is basically the product of the noise density times the frequency delta.
The results is shown in the graph below. Total Vrms = 23.2 uVrms for the frequency range 10Hz to 100KHz. This approximation is very close to the specified value of 20 uVrms.
I then looked as the specified noise of several common regulators and matched the values to the corresponding value of the LT1763 device.
A couple of observations: The LM340 is actually very good, in fact better than the beloved LM317 according to spec. The LM723 seems of lower noise than the LT1763, at least in the reported frequency range.
We can approximate the total noise Vrms for the 10Hz-100KHz interval by noticing that each frequency range contributes a percentage of the total noise. In the case of the LT1763, we notice that the 10Hz-10KHz range contributes about half of the total 10Hz-100KHz noise. The table below compares all the regulators in the 10Hz-100KHz range.
Here is a very good paper from TI explaining noise in linear regulators: [link]
According to the paper,
"The dominant source of noise in an LDO is usually theUnfortunately, it is not easy to access the bandgap output line in most integrated regulators...
bandgap. In most cases this is solved by adding a large
low-pass filter (LPF) to the bandgap output so that none
of the noise makes it into the gain stage."