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In this paper the dynamic element matching (DEM) technique is applied to a second generation current conveyor (CCII) in order to compensate the input offset and 1/f noise voltages. Apart from a residual clock-feedthrough error, a significant reduction in the offset voltage between CCII X and Y nodes is achieved with a slight increase in circuitry complexity. As an example, the dynamic-element matched CCII has been used for the design of a resistive sensor interface. Simulation results confirm theoretical results.

In this paper, we present a low-voltage (±0.75V) low-power (200μW) current-mode based integrated interface for the measure and heating control of resistive gas sensors. It is formed by two resistances, two improved CCIIs, which have been developed to achieve reduced parasitic components at its terminals, and a logic control block which both estimates the resistance sensor value (through a resistance-to-voltage conversion) and controls the temperature of the whole system.

In this paper we present an uncalibrated CMOS fully-integrable interface, based on oscillating topology, for wide-range resistive gas sensor applications. The proposed circuit is a low-voltage, low-cost and very simple front-end, able to reveal with good linearity and precision more than six decades of resistance variation and, at the same time, to estimate the sensor parasitic capacitance up to 50 pF. Moreover, the interface has also been designed, at transistor level, in a standard CMOS technology (AMS 0.35μm). In this case, no external resistors or capacitors are required, since passive component values are all integrable. This integrated solution has been developed so to be powered with a low supply voltage (2V) and to have characteristics independent both from supply variations and temperature drifts. This makes the proposed circuit suitable for portable applications. Preliminary experimental results, performed through a discrete element board fabricated with commercial components, have demonstrated the validity of the proposed interface and a good agreement between experimental results and theoretical values.

In this paper we propose a low supply voltage integrated lock-in amplifier, completely designed at transistor level and suitable for those sensor applications where the signal to be measured is buried into noise. The proposed system has been designed for operating with a 77 Hz reference signal and all its blocks have been internally designed, at transistor level and supplied at 2V, in a standard CMOS technology (AMS 0.35μm), so to have a completely integrated solution. Waiting for the chip fabrication, we have also developed and fabricated a lock-in system through a discrete element board with commercial components, for preliminary analysis. It has been proved that the system is able to recover with success signal from noise till to 0.1 S/N ratios without performance degradation: this corresponds to the detection of very small quantities of gas.

In this paper we propose a low-voltage low-power application of a quasi-ideal second generation current conveyor (CCII) as resistive sensor interface. The proposed architecture, which has been implemented using a standard CMOS 0.35μm process, consists of a single block oscillating circuit performing a resistance to period conversion. The same topology could be also used for capacitive sensor interfacing.

In this paper we propose a novel front-end, based on low voltage (LV) low power (LP) Second Generation Current Conveyors (CCIIs), for wide range resistive sensors, able to evaluate the resistive behaviour of the sensing element without any preliminary calibration. This interface operates a resistance-to-period (R-T) conversion exciting the sensor with a DC voltage and is able to reveal, for more than four decades of variation, both high and low resistive values. Post-layout simulations, conducted on the designed integrated solution, and preliminary experimental results, obtained using a commercial sensor (FIGARO TGS 2600) and AD844 as CCII, have shown high linearity and good agreement with theoretical expectations.

In this paper we present a new low voltage (1.5V supply) low power (750µW) capacitive sensor interface, based on a square wave oscillator implemented with a single second generation current conveyor (CCII). Complete theory calculations are addressed. Simulation results, obtained by means of Cadence simulator, are in a good agreement with theoretical expectations. Since the CCII has been implemented at transistor level, in a standard CMOS technology, the proposed sensor interface circuit can be completely integrated. The sensitivity of the conversion capacitance-oscillation period obtained from simulations is about 3ns/pF.

In this paper we propose a novel high precision current-mode instrumentation amplifier (CMIA), employing two second-generation current conveyors (CCIIs), which shows many advantages when compared to conventional differential architectures, for smart sensor system applications. In particular, in the proposed CMIA, the dynamic element matching (DEM) approach has been applied to a suitable CCII. This technique has allowed to decrease circuit offset due to mismatch of few components by dynamically interchanging them and averaging with a low pass filter, so avoiding any kind of CCII pre-calibration for offset compensation. Simulation results have demonstrated the validity of the present approach, in particular in sensor interface to increase system sensitivity.

In this paper we propose a novel fully-integrable oscillating circuit for the interfacing of high-valued Metal Oxide (MOX) resistive gas sensors, using a reduced number of active blocks. The proposed front-end employs only three Operational Amplifiers implementing a square wave oscillator whose output period is proportional to sensor resistance value. Through the use of an AC sensor excitation voltage, the circuit is able both to reveal typical resistive values of MOX gas sensors, which can vary from 100kΩ up to tens of GΩ, and to estimate also the parasitic capacitance in parallel to the resistive sensor (in the order of few pF). Preliminary experimental results, performed through a discrete component prototype and sample resistors, have shown high linearity and reduced percentage error (lower than 10%), compared with theoretical expectations.

We present a novel integrable Op Amp-based resistive sensor interface, performing a Resistance to Period (R-T) conversion and using a DC sensor excitation. The proposed circuit, based on an oscillator topology, is able to reveal more than four decades of high resistance variations (from about 1MΩ to more than 10GΩ), typical of some resistive gas sensors (e.g., metal oxide, MOX, sensors), avoiding the estimation of the sensor parallel capacitive component (in the order of few pF), since a DC excitation voltage for the resistive sensor has been utilized. The proposed front-end has been designed, as integrated circuit, in a standard CMOS technology (AMS 0.35µm), with a dual-supply voltage (±1.65V), so to be suitable in low-cost portable applications. Post-schematic simulations, on the designed integrated solution, and experimental results, obtained from a preliminary discrete-component prototype, have both shown high linearity and reduced percentage error (in the order of few %), with respect to the calculated theoretical values.