G. Scandurra

Electrical Characterization and Hydrogen Peroxide Sensing Properties of Gold/Nafion:Polypyrrole/MWCNTs Electrochemical Devices

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.

How to enlarge the bandwidth without increasing the noise in OP-AMP-based transimpedance amplifier

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

An ultralow noise preamplifier for low frequency noise measurements

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 kohms.

DEDICATED INSTRUMENTATION FOR HIGH SENSITIVITY, LOW FREQUENCY NOISE MEASUREMENT SYSTEMS

Low Frequency Noise Measurements (LFNM) can be used as very sensitive tool for the characterization o f the quality and the reliability of electron devices. However, especially in those cases in which the frequency range of interest extends below 1 Hz, instrumentation with an acceptable low level of background noise is not e asily found on the market. In fact, at very low frequencies, the flicker noise introduced by the electronic components which make up the instrumentation becomes predominant and several interesting phenomena which could be detected by means of LFNM may result completely hidden in the background noise. This consideration is not limited to the case of input preamplifiers but does extend to any piece of instrumentation that contributes to the LFNM systems, and in particular to the power supplies used for biasing the Device Under Test. During the last few years, our research groups have been strongly involved in the design of very low noise instrumentation for application in the field of LFNM. In this work we report the main results which we have ob tained together w ith a discussion of the d esign guidelines that have a llowed us, in a few cases, to reach noise levels not to be equalled by any instrumentation available on the market.

Ultraflexible Tactile Piezoelectric Sensor Based on Low-Temperature Polycrystalline Silicon Thin-Film Transistor Technology

In this paper, we present an ultraflexible tactile sensor, in a piezo-eletricoxide-semiconductor FET configuration, composed by a poly[vinylidenefluoride-co-trifluoroethylene] capacitor with an embedded readout circuitry, based on nMOS polysilicon electronics, integrated directly on polyimide. The ultraflexible device is designed according to an extended gate configuration. The sensor exhibits enhanced piezoelectric properties, thanks to the optimization of the poling procedure (with electric field up to 3 MV/cm), reaching a final piezoelectric coefficient d33 of 47 pC/N. The device has been electromechanically tested by applying perpendicular forces with a minishaker. The tactile sensor, biased in a common-source arrangement, shows a linear response to increasing sinusoidal stimuli (up to 2 N) and increasing operating frequencies (up to 1200 Hz), obtaining a response up to 430 mV/N at 200 Hz for the sensor with the highest value of d33. The sensor performances were also tested after several cycles of controlled bending in different amount of humidity with the intent to investigate the device behavior in real conditions.

A New Circuit Topology for the Realization of Very Low-Noise Wide-Bandwidth Transimpedance Amplifier

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.

R-/spl beta/R ladder networks for the design of high-accuracy static analog memories

In this paper, we show that the topology of successive approximation analog-to-digital converters can be used for the realization of a static analog memory (SAM), that is a circuit capable of indefinitely maintaining at its output a voltage close to the one presented at its input for a limited time. After demonstrating that the accuracy which can be obtained in the storage process is limited by the maximum positive value of the differential nonlinearity of the digital-to-analog converter (DAC) used as part of the circuit, we demonstrate that by means of a proper choice of the ratio of the resistances of the ladder network of the DAC, very high accuracy can be obtained even by employing poor tolerance resistors, without the need for any trimming or calibration step. This fact might be advantageously exploited for the design of integrated multichannel SAMs which, employed in connection with a single high-accuracy DAC, could allow the realization of multiple output, high-accuracy, programmable voltage or current sources.

Electrochemical Detection of p-Aminophenol by Flexible Devices Based on Multi-Wall Carbon Nanotubes Dispersed in Electrochemically Modified Nafion

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 μA·(μM−1)·cm−2.

Automatic measurement system for the DC and low-f noise characterization of FETs at wafer level

In this work we propose a measurement setup topology suitable for the automatic DC and low frequency noise (LFN) characterization of field effect transistors at wafer level. The system is composed of source and measure units (SMUs), by a custom-built low noise amplifier (LNA), and by a PC based spectrum analyzer. No bias filters and switch matrices are used, allowing fast switching between DC and LFN measurements together with low leakage. The programmable LNA can reach background noise levels in the order of fA/Hz1/2, while DC performances are limited by the SMUs. The main feature of the proposed system is the high degree of operational flexibility due to the complete PC-based software control. LFN characterization, down to bias DC currents of 1pA, in organic thin film transistors is reported to demonstrate system operation and performances.

Differential ultra low noise amplifier for low frequency noise measurements

Almost all low noise voltage preamplifier suitable for application in the field of Low Frequency Noise Measurements (either commercially available or proposed in the literature) are single ended input amplifiers. This means that one end of the measuring port of the Device Under Test (DUT) must be connected to common ground. This may be a severe limitation in many interesting measurement configurations, such as the case in which Kelvin connections to the DUT must be employed. In this paper we propose a simple design of a fully differential input ultra low noise amplifier with noise performances, in term of equivalent input voltage noise, comparable to those of the best single ended input amplifiers for low frequency noise measurements reported in the literature. Indeed, the amplifier we propose is characterized by a voltage gain of 80 dB, in the bandwidth from a few tens of mHz up to a few kHz, and by an equivalent input voltage noise as low as 14 nV/√Hz (100 mHz), 2 nV/√Hz (1 Hz), 1.2 nV/√Hz (10 Hz) and 1...