3 Conclusion

This technical white paper discussed the noise measurement basics of LDOs while using a spectrum analyzer. The document also discussed the requirements to design an extremely low-noise amplifier circuit necessary for measuring the noise of an ultra-low noise LDO. The designed amplifier circuit benefits from the parallel op-amp technique discussed in the References [3] section to lower the input referred noise of the amplifier. This significant reduction in the input noise makes this amplifier design a vital tool for amplifying tiny signals within the BW of 3Hz–10MHz. Additionally, to improve the noise floor measurement for any spectrum analyzer, the amplifier circuit can also be used to improve the noise floor measurement of any network analyzer.

The use of a ceramic capacitor as a filter for blocking DC enables the amplifier to work with noise (tiny signals) that has a positive or negative offset voltage.