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The Internet of Things (IoT) is gaining more and more popularity and it is establishing itself in all areas, from industry to everyday life. Given its pervasiveness and considering the problems that afflict today's world, that must be carefully monitored and addressed to guarantee a future for the new generations, the sustainability of technological solutions must be a focal point in the activities of researchers in the field. Many of these solutions are based on flexible, printed or wearable electronics. The choice of materials therefore becomes fundamental, just as it is crucial to provide the necessary power supply in a green way. In this paper we want to analyze the state of the art of flexible electronics for the IoT, paying particular attention to the issue of sustainability. Furthermore, considerations will be made on how the skills required for the designers of such flexible circuits, the features required to the new design tools and the characterization of electronic circuits are changing. [ABSTRACT FROM AUTHOR]

Abstract-In this paper, we discuss the possibility of realizing high-accuracy digital-analog (DA) converters by exploiting the properties of R/βR(β > 2) ladder networks. Extensive simulations demonstrate that, if a proper value of β is chosen, high accuracy can be obtained by resorting to a very simple self-calibration algorithm. This is true, even in the case of large tolerance values for the resistors that make up the ladder network. Such a result may allow the design of a high-accuracy very low cost converter. The effect of the offset of the comparator needed for the self-calibration algorithm is also discussed. [ABSTRACT FROM AUTHOR]

The properties of a differential transconductance amplifier coupled with a four channel measurement system are exploited in order to reach a very high sensitivity in current noise measurements. In particular, it is demonstrated that, in proper conditions, the noise contributions coming from the active and passive devices that make up the transresistance amplifier can be virtually eliminated. Moreover, the proposed measurement method allows the evaluation of the impedance of the device under test from noise measurement data. Actual measurement results are also reported that demonstrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

In this paper, after discussing some important limitations of the most common circuital configuration that is used for the realization of very low-noise transimpedance amplifiers, we propose and analyze a new circuit topology which allows us to obtain significant advantages as far as equivalent input current noise and bandwidth (BW) are concerned. We present a simple circuit implementation of the new transimpedance amplifier, together with the results of its noise characterization. The comparison between these measurements and those obtained on a conventional transimpedance amplifier with the same transimpedance gain has confirmed that the proposed approach allows us to obtain a lower background noise and a larger BW for the same transimpedance gain. [ABSTRACT FROM AUTHOR]

In this paper, the authors demonstrate that a proper connection of two or more low-cost low-accuracy digital-analog converters can be used for the realization of a high-accuracy static analog memory (SAM). High-accuracy SAM is a circuit behaving as a high-accuracy sample and hold block with indefinite hold capability. The proposed topology can be applied both at the board level and at the integrated-circuit level when designing compact and low-cost devices for automated test equipment. In fact, as it will be demonstrated in this paper, high accuracy can be guaranteed by design, without the need for any calibration procedure. The proposed approach can therefore be considered as a possible and advantageous alternative to the conventional methods employed for the realization of high-accuracy multiple-output programmable voltage or current sources. A prototype of the SAM, based on the proposed approach, has been assembled and tested. As it will be shown, the obtained experimental results fully confirm the validity of the approach. [ABSTRACT FROM AUTHOR]

Increasing the bandwidth without degrading the noise performance represents the main challenge in the design of transimpedance amplifiers. This paper presents a novel circuit topology for a transimpedance amplifier that allows obtaining an improved tradeoff between equivalent input noise and bandwidth with respect to the conventional approach. The effectiveness of the new topology has been demonstrated by designing and testing a prototype of a transimpedance amplifier based on the proposed topology. [ABSTRACT FROM AUTHOR]

Low-frequency noise measurements represent an interesting investigation technique for the characterization of the quality and reliability of microelectronic materials and devices. Performing meaningful noise measurements at low and very low (f < Hz) frequencies, however, may be quite challenging, particularly because of the many sources of interferences that superimpose to the noise signal. For this reason packaged samples are preferred because they allow accurate shielding from the external environment, and because keeping the sample in close proximity to the low-noise biasing system and amplifier reduces microphonic and electromagnetic disturbances. Notwithstanding this, the possibility of performing low-frequency noise measurements at wafer level would be quite interesting, both because of the ease of obtaining wafer-level samples from industries with respect to packaged samples, and because this would avoid possible packaging-process induced device degradation. The purpose of this work is to demonstrate that it is, in fact, possible to design and build a dedicated probe system for performing high-sensitivity, low-frequency noise measurements on metal-oxide--semiconductor devices at wafer level. [ABSTRACT FROM AUTHOR]

Shows that the topology of successive approximation analog-to-digital converters can be used for the realization of a static analog memory. Capability of the circuit to indefinitely maintain at its output a voltage close to the one presented at its input for a limited time; Limitation of accuracy by the maximum positive value of the differential nonlinearity of the digital-to-analog converter.

Presents information on a study which described a method for high-sensitivity noise measurement systems. Proposed measurement method; Experimental results; Conclusions.

Presents information on a study which described a high-stability temperature-controlled oven for low-frequency noise measurements. Design guidelines and realization; Results and discussion; Conclusions.

Presents information on a study which focused on the design and principle of operation of a measurement system for performing reliability tests on metallic interconnections of integrated circuits. Conventional median time to failure (MTF); Test setups; True constant temperature MTF test; Conclusions.

Presents the findings of a study on the sources of ulta low-noise currents. Why the solid state direct current sources on the market are not suitable for applications in low noise measurements; Information on the case of low-frequency noise in such instruments; Description of the instrument; Usage of a circuit topology in which the solid-state voltage reference has been substituted by a low-noise battery; Further details on the study.

Presents a study which describes the design, realization and test of a multichannel ultralow-noise data acquisition system. Instrument designed for performing low-frequency noise measurements on interconnect lines of an integrated circuit.

Summarizes the noise and flunctuation in submicrometric Al-Si interconnect lines. Characteristics of low-frequency noise (LFN) in metals; Sample description and experiments; Analysis of the experimental data; Discussion on LFN in metal lines; Conclusion.

Testing the shielding effectiveness of materials is a key step for many applications, from the industrial to the biomedical field. This task is very relevant for high-sensitivity sensors, whose performance can be greatly affected by electromagnetic fields. However, the available testing procedures often require expensive, bulky, and heavy measurement chambers. In this paper, a cost-effective and reliable measurement procedure for testing the shielding effectiveness of materials is proposed. It exploits a lab-scale anechoic shielded chamber, which is lightweight, compact, and cost-effective if compared to the available commercial solutions. The measurement procedure employs a vector network analyzer to allow an accurate and fast characterization setup. The chamber realization phases and the measurement procedure are described. The shielding capability of the chamber is measured up to 26 GHz, whereas the performance of commercial shielding coatings is tested to demonstrate the measurement's effectiveness. [ABSTRACT FROM AUTHOR]

We discuss the implementation challenges of gas sensing systems based on low-frequency noise measurements on chemoresistive sensors. Resistance fluctuations in various gas sensing materials, in a frequency range typically up to a few kHz, can enhance gas sensing by considering its intensity and the slope of power spectral density. The issues of low-frequency noise measurements in resistive gas sensors, specifically in two-dimensional materials exhibiting gas-sensing properties, are considered. We present measurement setups and noise-processing methods for gas detection. The chemoresistive sensors show various DC resistances requiring different flicker noise measurement approaches. Separate noise measurement setups are used for resistances up to a few hundred kΩ and for resistances with much higher values. Noise measurements in highly resistive materials (e.g., MoS2, WS2, and ZrS3) are prone to external interferences but can be modulated using temperature or light irradiation for enhanced sensing. Therefore, such materials are of considerable interest for gas sensing. [ABSTRACT FROM AUTHOR]

Solid-state supercapacitors with areal capacitance in the order of 100 mF⋅cm−2 are developed on paper substrates, using eco-friendly, low-cost materials and a simple technology. The electrochemically active material used as the electrode is prepared from a stable water-based ink, obtained by doping commercial polypyrrole (PPY) powder with dodecylbenzene sulfonic acid (DBSA), and characterized by optical and electrical measurements, Raman investigation and Atomic Force Microscopy. The PPY:DBSA ink can be directly applied on paper by means of rechargeable water pens, obtaining, after drying, electrically conducting solid state tracks. The PPY:DBSA layers are then interfaced to one another through a polymer gel based on potassium hydroxide and chitosan, acting both as the ion-conducting medium and as the separator. The areal capacitance of the devices developed by following such a simple rule can be improved when the PPY:DBSA ink is applied in combination with other nanostructured carbon material. [ABSTRACT FROM AUTHOR]

Electrochemical dissolution of metallic copper into slightly acidic aqueous solutions of chitosan yields a clear and stable dispersion of Copper Oxide nanoparticles into the organic polymer host. The electrochemically synthesized chitosan:CuOx nanocomposite is characterized by means of spectrophotometry, frequency domain electrical measurements and morphological analysis. Solid state electrochemical cells having pure chitosan as the electrolyte and using chitosan:CuOx as the electrode, are developed and characterized by means of electrical measurements performed in the ±1 V voltage window. The current-voltage loops of the cells, measured in deionized water, are found to reversibly change in response to hydrogen peroxide added to the water in 0.2 μM subsequent steps. Such changes, clearly distinguishable from changes recorded in response to other analytes, can be exploited in order to develop a hydrogen peroxide sensor able to work without the need for any supporting electrolyte. [ABSTRACT FROM AUTHOR]

A conducting composite prepared by dispersing multi-walled carbon nanotubes (MWCNTs) into a host matrix consisting of Nafion, electrochemically doped with copper, has been prepared, characterized and used to modify one of the gold electrodes of simply designed electrochemical cells having copier grade transparency sheets as substrates. Electrical measurements performed in deionized water show that the Au/Nafion/Au-MWCNTs--Nafion:Cu cells can be successfully used in order to detect the presence of p-aminophenol (PAP) in water, without the need for any supporting electrolyte. The intensity of the redox peaks arising when PAP is added to deionized water is found to be linearly related to the analyte in the range from 0.2 to 1.6 µM, with a detection limit of 90 nM and a sensitivity of 7 µ A· (µM-1 )· cm-2. [ABSTRACT FROM AUTHOR]

In this paper an approach for designing a programmable, very low noise, high accuracy voltage source for biasing devices under test in low frequency noise measurements is proposed. The core of the system is a supercapacitor based two pole low pass filter used for filtering out the noise produced by a standard DA converter down to 100 mHz with an attenuation in excess of 40 dB. The high leakage current of the supercapacitors, however, introduces large DC errors that need to be compensated in order to obtain high accuracy as well as very low output noise. To this end, a proper circuit topology has been developed that allows to considerably reduce the effect of the supercapacitor leakage current on the DC response of the system while maintaining a very low level of output noise. With a proper design an output noise as low as the equivalent input voltage noise of the OP27 operational amplifier, used as the output buffer of the system, can be obtained with DC accuracies better that 0.05% up to the maximum output of 8 V. The expected performances of the proposed voltage source have been confirmed both by means of SPICE simulations and by means of measurements on actual prototypes. Turn on and stabilization times for the system are of the order of a few hundred seconds. These times are fully compatible with noise measurements down to 100 mHz, since measurement times of the order of several tens of minutes are required in any case in order to reduce the statistical error in the measured spectra down to an acceptable level. [ABSTRACT FROM AUTHOR]

Electrical noise sources are basic building blocks in many measurement and instrumentation applications and in communication systems. In this paper, we propose a quite simple topology for the realization of a programmable, wide bandwidth, white noise current source that requires only two resistors and one operational amplifier. We validate the proposed approach by means of SPICE simulations and demonstrate, by means of proper measurements, the capability of generating a flat current noise spectrum in a frequency range up to four decades from a few Hz up to 100 kHz. [ABSTRACT FROM AUTHOR]

• transformer based amplifier can be used to measure noise in low-ohmic IR detectors. • transformer primary winding thermal noise can be reduced using cross-correlation. • transformers and cross correlation provide for low noise at low frequencies. • system noise of 100 pV/√Hz@1 Hz can be obtained after 60 min of cross-correlation. The paper presents a noise measurement system particularly suited for the investigation of the low frequency noise in advanced infrared (IR) detectors characterized by low shunt resistance. By combining the performances of ultra-low noise amplifiers with the advantages that can be obtained by transformer input coupling and cross-correlation between two nominally identical channels, we were able to obtain excellent noise performances in the low frequency region (below 10 Hz). Indeed, the equivalent input background noise that can be obtained with the approach we propose can be as low as 1 × 10-20 V2/Hz (≈100 pV/√Hz) at 1 Hz. The system was tested using source resistances in the range from 1 to 10 Ω as well as actual advanced IR detectors to demonstrate its ability to provide information about the noise generated at very low frequencies. [ABSTRACT FROM AUTHOR]

In this paper, the design of a new offset correction system employing a time-varying resistance as a probe for the detection of the sign and magnitude of the equivalent input offset of an operational amplifier in a series–shunt feedback configuration is presented. In order to considerably reduce the charge injection effects resulting from the switching of the MOS transistor that is used for the implementation of the time-varying resistance, we resort to a proper discrete time-sampling strategy for offset error detection. With respect to a previous topology, the new approach allows us to extend the useful amplifier bandwidth from a few hertz up to about 100 Hz with a gain boost from 201 to 1001. With the new approach, a residual offset on the order of a few tens of nanovolts is obtained, which allows us to classify the system as a nanovolt amplifier. [ABSTRACT FROM AUTHOR]

In this paper, we discuss a few techniques that allow an effective reduction of the background noise and/or the reduction of the measurement time when performing voltage noise measurements by employing a number of nominally identical voltage amplifiers with negligible equivalent input current noise. It is demonstrated in particular that, if N\ (N > 2) voltage amplifiers are connected to the device under test and if the properties of cross-correlation among all N acquisition channels connected to the output of each amplifier are exploited, the time required for obtaining a given accuracy is reduced by a factor N(N - 1)/2 with respect to the conventional setup for cross-correlation that employs only two channels. From another point of view, the effective background noise is reduced for constant measurement time. Such a factor can be further increased if amplifier paralleling is also employed for reducing the equivalent input voltage noise for each channel. Measurements on two different setups employing up to four channels and up to eight channels are presented that confirm the expected reduction factors in measurement times. [ABSTRACT FROM AUTHOR]

Electrochemical devices using as substrates copier grade transparency sheets are developed by using ion conducting Nafion:polypyrrole mixtures, deposited between gold bottom electrodes and upper electrodes based on Multi Walled Carbon Nanotubes (MWCNTs). The electrical properties of the Nafion:polypyrrole blends and of the gold/Nafion:polypyrrole/MWCNTs devices are investigated under dry conditions and in deionized water by means of frequency dependent impedance measurements and time domain electrical characterization. According to current-voltage measurements carried out in deionized water, the steady state current forms cycles characterized by redox peaks, the intensity and position of which reversibly change in response to H2O2, with a lower detection limit in the micromolar range. The sensitivity that is obtained is comparable with that of other electrochemical sensors that however, unlike our devices, require supporting electrolytes. [ABSTRACT FROM AUTHOR]

A new topology for the implementation of a very low offset voltage preamplifier is presented. The new topology employs a time-varying resistance as a probe for detecting the sign and magnitude of the equivalent input offset of an operational amplifier in a series-shunt feedback configuration and allows for continuously correcting the offset voltage by means of a proper control feedback. The most remarkable feature of the approach we propose is the fact that the offset correction can continuously be performed with the signal voltage source connected to the circuit, as its presence and magnitude do not affect the offset detection circuit. At the same time, the offset cancellation circuit has minimum effect on the output voltage of the preamplifier in the bandwidth of the signal. An actual low-offset preamplifier based on the new approach we propose has been built and tested. While employing a metal-oxide-semiconductor field-effect transistor (MOSFET) input operational amplifier with a typical input offset of 100 μV (600- μV maximum), a voltage preamplifier with a gain of 201 and an equivalent input offset voltage below 100 nV is consistently obtained, which is independent, by design, of the temperature. While characterized by these excellent performances, the system employs quite standard low-cost components and does not require any calibration procedure. [ABSTRACT FROM AUTHOR]

Low frequency noise measurements are among the most sensitive tools for the investigation of the quality and of the reliability of semiconductor devices. The sensitivity that can be obtained depends on the background noise of the low noise preamplifier coupled to the device under test (DUT) that, at very low frequencies, is dominated by flicker noise. The low frequency noise produced by the DUT, on the other end, is very often the most interesting signal to be detected and analyzed. In this work we propose a very simple topology for the realization of a general purpose low noise preamplifier whose noise performances, at very low frequencies (below 10 Hz), are significantly better than those that can be obtained by the most popular commercial instrumentation. Indeed, a gain of 80 dB with a pass band extending from a few tens of mHz up to a few kHz with an equivalent input voltage noise as low as 14 nV/[Square_Root]Hz (100 mHz), 1.4 nV/[Square_Root]Hz (1 Hz), 1.0 nV/[Square_Root]Hz (10 Hz), and 0.8 nV/[Square_Root]Hz (1 kHz) are consistently obtained by using quite standard electronic components and with no need for trimming and/or calibration steps. Moreover, the junction field-effect transistor input stage of the amplifier is characterized by an equivalent input current noise below 4 fA/[Square_Root]Hz in the entire bandwidth, resulting in negligible background noise degradation for DUT impedances in excess of 100 kΩ. [ABSTRACT FROM AUTHOR]

• Voltage noise measurements are better for low resistance DUT comparing current ones. • Cross-correlation with ultra-low noise amplifiers reduces measurement time. • Logarithmic Spectrum Analyzer provides few frequency decades noise measurements. • Noise measurements of biased low-resistance InAsSb detectors are possible. The paper presents a system for noise measurements in infrared photodetectors characterized by low shunt resistances based on a two-channel ultra-low-noise voltage amplifier with paralleled discrete JFETs at the input stages. Using cross correlation method, a background noise well below of 10−19 V2/Hz can be obtained at frequencies above 10 Hz. To facilitate the estimation of the noise in such a wide frequency range (5 decades), we also developed a software based on the QLSA library. As a result of these efforts, the equivalent input voltage noise of the system is below 10−19 V2/Hz at 10 Hz and 10−20 V2/Hz for frequencies above a few hundred Hz. The system effectiveness is demonstrated by noise measurements at room temperature on advanced InAs x Sb 1-x photodetectors characterized by an active area of 1 mm2 and a shunt resistance below 10 Ω. [ABSTRACT FROM AUTHOR]

Flexible energy storage devices and supercapacitors in particular have become very attractive due to the growing demand for wearable consumer devices. To obtain supercapacitors with improved performance, it is useful to resort to hybrid electrodes, usually nanocomposites, that combine the excellent charge transport properties and high surface area of nanostructured carbon with the electrochemical activity of suitable metal oxides or conjugated polymers. In this work, electrochemically active conducting inks are developed starting from commercially available polypyrrole and graphene nanoplatelets blended with dodecylbenzenesulfonic acid. Films prepared by applying the developed inks are characterized by means of Raman measurements, Fourier Transform Infrared (FTIR) analysis, and Atomic Force Microscopy (AFM) investigations. Planar supercapacitor prototypes with an active area below ten mm2 are then prepared by applying the inks onto transparency sheets, separated by an ion-permeable nafion layer impregnated with lithium hexafluorophospate, and characterized by means of electrical measurements. According to the experimental results, the devices show both pseudocapacitive and electric double layer behavior, resulting in areal capacitance that, when obtained from about 100 mF⋅cm−2 in the sample with polypyrrole-based electrodes, increases by a factor of about 3 when using electrodes deposited from inks containing polypyrrole and graphene nanoplateles. [ABSTRACT FROM AUTHOR]

This article describes a method for voltage noise measurements with a sensitivity superior to that of conventional methods. This is obtained by resorting to an original three-channel amplifier configuration and by following a four-step measurement procedure. A comparative analysis of this method and the conventional cross-correlation technique is presented. SPICE simulations and noise measurements performed on a prototype circuit demonstrate the validity of the proposed approach. [ABSTRACT FROM AUTHOR]

Ultralow noise measurements often require the application of signal processing and correction techniques to go beyond the noise performances of front-end amplifiers. In this paper, a new method for the voltage noise measurement is proposed, which allows, at least in principle, the complete elimination of the noise introduced by the amplifiers used for the measurements. This is obtained by resorting to the conventional cross-correlation technique for the elimination of the contribution of the equivalent input voltage noise of the amplifiers and by using a new three- step-measurement procedure that exploits different amplifier-configuration measurements in order to subtract the contribution of the equivalent input current noise of the amplifiers. [ABSTRACT FROM AUTHOR]

Presents a paper which presented the construction, design and testing of an ultralow-noise programmable voltage source (ULNPVS), as an alternative for low-frequency noise measurements. Examination of the ultralow-noise programmable voltage source; Main objectives of the design; How introducing additional noise sources for low frequency noise measurements is avoided.

Low-frequency noise measurements have long been recognized as a valuable tool in the examination of quality and reliability of metallic interconnections in the microelectronic industry. While characterized by very high sensitivity, low-frequency noise measurements can be extremely time-consuming, especially when tests have to be carried out over an extended temperature range and with high temperature resolution as it is required by some advanced characterization approaches recently proposed in the literature. In order to address this issue we designed a dedicated system for the characterization of the low-frequency noise produced by a metallic line vs temperature. The system combines high flexibility and automation with excellent background noise levels. Test temperatures range from ambient temperature up to 300°C. Measurements can be completely automated with temperature changing in pre-programmed steps. A ramp temperature mode is also possible that can be used, with proper caution, to virtually obtain a continuous plot of noise parameters vs temperature. [ABSTRACT FROM AUTHOR]

Equivalent input current noise and bandwidth are the most relevant parameters qualifying a low-noise transimpedance amplifier. In the conventional topology consisting of an operational amplifier in a shunt-shunt configuration, the equivalent input noise decreases as the feedback resistor ( RF), which also sets the gain, increases. Unfortunately, as RF increases above a few MΩ, as it is required for obtaining high sensitivity, the bandwidth of the system is set by the parasitic capacitance of RF and reduces as RF increases. In this paper, we propose a new topology that allows overcoming this limitation by employing a large-bandwidth voltage amplifier together with a proper modified feedback network for compensating the effect of the parasitic capacitance of the feedback resistance. We experimentally demonstrate, on a prototype circuit, that the proposed approach allows to obtain a bandwidth in excess of 100 kHz and an equivalent input noise of about 4 fA/ [ABSTRACT FROM AUTHOR]

In this paper, complementary measurements of the drain and the gate low-frequency noise are used as a powerful probe for sensing the hafnium-related defects in nMOSFETs with high-k gate stacks and polysilicon gate electrode. Drain noise measurements indicate that for low hafnium content (23%) and thin high-k thickness (2 nm), the defect density at the substrate/dielectrics interface is similar to the case of conventional SiO2. Gate-noise measurements suggest that the defect density in the bulk of the high-k gate stacks and at the gate/dielectrics interface is strongly degraded by the hafnium content. [ABSTRACT FROM AUTHOR]

The main requirement for using the Fluctuation Enhanced Sensing technique is the ability to perform low-frequency noise measurements. The portability of the measurement system is also a quite desirable feature not limited to this specific application. In this paper, an approach for the realization of a dual channel spectrum analyzer that is capable of exploring frequencies down to DC, although based on a USB sound card, is proposed. The lower frequency range of the input signals, which is outside the frequency range of the sound board, is upconverted to higher frequencies by means of a very simple modulation board. Then, the entire spectrum is reconstructed numerically by proper elaboration. With the exception of the modulation board, the approach we propose does not rely on any specific hardware. Thanks to the efficiency of the spectra estimation and reconstruction software, which is based on a public domain library, the system can be built on a low-cost computer single board computer, such as the Raspberry PI3. Moreover, when equipped with an optical TCP/IP link, it behaves as a compact spectrum analyzer that along with the device under test can be placed into a shielded environment, thus being isolated from external electromagnetic interferences. [ABSTRACT FROM AUTHOR]