How is the output noise spectral density of an ultra-low noise LDO measured?

Q

A

Noise measurement equipment such as the Agilent E5505A or E5052B forms the
basis of the noise test fixture. Since the output voltage noise of the
ADM7150/ADM7151 is nearly as low and the noise floor of the test equipment the
noise measurement test set is used in conjunction with a high gain, ultra-low
noise, wide bandwidth preamplifier. The input referred noise of the
preamplifier is less than 350pV/√Hz from approximately 100Hz to 10MHz.