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.
Studies of electrical properties, including noise properties, of thick-film resistors prepared from various resistive and conductive materials on LTCC substrates have been described. Experiments have been carried out in the temperature range from 300 K up to 650 K using two methods, i.e. measuring (i) spectra of voltage fluctuations observed on the studied samples and (ii) the current noise index by a standard meter, both at constant temperature and during a temperature sweep with a slow rate. The 1/f noise component caused by resistance fluctuations occurred to be dominant in the entire range of temperature. The dependence of the noise intensity on temperature revealed that a temperature change from 300 K to 650 K causes a rise in magnitude of the noise intensity approximately one order of magnitude. Using the experimental data, the parameters describing noise properties of the used materials have been calculated and compared to the properties of other previously studied thick-film materials.
Studies of noise properties of thick-film conducting lines from Au or PdAg conductive pastes on LTCC or alumina substrates are reported. Experiments have been carried out at the room temperature on samples prepared in the form of meanders by traditional screen-printing or laser-shaping technique. Due to a low resistance of the devices under test (DUTs), low-frequency noise spectra have been measured for the dc-biased samples arranged in a bridge configuration, transformer-coupled to a low-noise amplifier. The detailed analysis of noise sources in the signal path and its transfer function, including the transformer, has been carried out, and a procedure for measurement setup self-calibration has been described. The 1/f noise component originating from resistance fluctuations has been found to be dominant in all DUTs. The analysis of experimental data leads to the conclusion that noise is produced in the bends of meanders rather than in their straight segments. It occurs that noise of Au-based laser-shaped lines is significantly smaller than screen-printed ones. PdAg lines have been found more resistive but simultaneously less noisy than Au-based lines.