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