The intrinsic noise of giant magnetoresistive (GMR) sensors is large at low frequencies, and their resolution is inevitably significantly limited. Investigation of GMR noise requires the use of measurement systems that have lower noise than the sample. In this context, the main purpose of this study is to evaluate the effectiveness of two electronic noise measurement configurations of a single GMR sensing element. The first method connects the sample in a voltage divider configuration and the second method connects in a Wheatstone bridge configuration. Three amplification set-ups were investigated: a low-noise amplifier, an ultra-low-noise amplifier and an instrumentation amplifier. Using cross-correlation, the noise of the measurement system introduced by the amplifiers was reduced. Noise spectra were recorded at room temperature in the frequency range of 0.5 Hz to 10 kHz, under different sample bias voltages. The measurements were performed in zero applied magnetic field and in a field corresponding to the maximum sensitivity of the sensor. From the noise spectra, the detectivity of the sensor was determined to be in the 200–300 nT/√Hz range. Good agreement was observed between the results obtained using all three set-ups, suggesting the effectiveness of the noise measurement systems applied to the magnetoresistive sensor.

In this work two PSpice models for a current sensor based on spin-valve magnetoresistive microstructures are described and validated. The magnetic spin-valves are patterned, optimized, and characterized in terms of magnetoresitive ratio, sensitivity, and linearity. Starting from the experimental characteristics of the sensor, the first model is implemented using LookUp Table method, which is a table-based approach to the empirical modeling. The second proposed model is based on the analytical description of the experimental characteristic of the sensor and the implementation of the higher order polynomial in PSpice. Experimental data were interpolated in MATLAB using the spline curve which was fitted with polynomials of different orders and the coefficients are used as input data in the PSpice model. Once the designed PSpice models are validated, they can be successfully used to model the behavior of other types of magnetoresistive structures and may be easily adaptable to integrated sensors produced by industrial manufacturers.

The properties of solution-derived nickel oxide (NiO) thin films are strongly influenced by precursor chemistry and post-deposition thermal treatment. In this work, NiO thin films were deposited on indium tin oxide (ITO)-coated glass substrates by chemical solution deposition using a spin-coating process. A 0.6 M nickel acetylacetonate-derived precursor solution prepared in a methanol–propionic acid solvent system was used as the starting solution. The films were thermally treated at 600 °C under continuous oxygen flow, with annealing holding times of 2, 4, and 6 h, to evaluate the effect of thermal-treatment duration on phase formation, surface morphology, and electrochemical redox behavior. Thermal and infrared analyses confirmed precursor decomposition and the formation of nickel–oxygen bonding after thermal conversion. X-ray diffraction confirmed the formation of single-phase cubic NiO at all holding times, while quantitative peak analysis indicated a modest increase in crystallite size from 12.4 to 13.9 nm with prolonged annealing. Atomic force microscopy revealed continuous and homogeneous film surfaces, with low root-mean-square roughness values in the range of 2.5–2.7 nm. Cyclic voltammetry in a LiClO₄/propylene carbonate electrolyte showed a reversible redox response associated with the Ni²⁺/Ni³⁺ transition, accompanied by visible switching between bleached and colored states. The results indicate that annealing holding time affects the structural and morphological characteristics of spin-coated NiO thin films, while the electrochemical measurements confirm reversible redox activity in the investigated sample. These findings provide a processing-oriented basis for evaluating thermal-treatment conditions in solution-derived NiO films intended for electrochemical and optical modulation applications.

This paper investigates a method of excluding the input decoupling capacitors in an AC coupled instrumentation amplifier. The idea behind this paper is focusing mainly on reducing the silicon area when designing such amplifiers or the number of needed external components. Especially when the design requirements are pointed to low frequency operation but keeping AC coupling in the same time, the reactive components values may noticeably increase. As long as the GIC, Generalized Impedance Circuits, more specific the gyrators, are able to replace the capacitive and inductive behavior, they represent a good reason to study their applicability within instrumentation amplifiers. The gyrators are built around operational amplifiers so there will be a tradeoff between complexity in terms of transistor number and saved space by eliminating the capacitors at the input. The concept has been designed and validated based on simulation results using LtSpice.