Abstract
Measurement of low-frequency noise properties of modern electronic
components is a very demanding challenge due to the low magnitude of a
noise signal and the limit of a dissipated power. In such a case, an ac
technique with a lock-in amplifier or the use of a low-noise transformer
as the first stage in the signal path are common approaches. A software
dual-phase virtual lock-in (VLI) technique has been developed and tested
in low-frequency noise studies of electronic components. VLI means that
phase-sensitive detection is processed by a software layer rather than by
an expensive hardware lock-in amplifier. The VLI method has been tested in
exploration of noise in polymer thick-film resistors. Analysis of the
obtained noise spectra of voltage fluctuations confirmed that the 1/f
noise caused by resistance fluctuations is the dominant one. The
calculated value of the parameter describing the noise intensity of a
resistive material, C = 1·10−21 m3, is consistent with that obtained with
the use of a dc method. On the other hand, it has been observed that the
spectra of (excitation independent) resistance noise contain a 1/f
component whose intensity depends on the excitation frequency. The
phenomenon has been explained by means of noise suppression by impedances
of the measurement circuit, giving an excellent agreement with the
experimental data.
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