Massimo Piotto

Design of CMOS chopper amplifiers for thermal sensor interfacing

An analytical approach to the design of compact CMOS chopper amplifiers for integrated thermoelectric sensors is presented. The impact of the high resistance and low signal bandwidth of thermopile sources on the design is illustrated. The proposed approach, regarding the precision vs noise tradeoff, is applied to the design of a practical prototype, using a commercial process. Accurate electrical simulations are provided to confirm the effectiveness of the proposed design methodology.

Acoustic Velocity Sensors with Programmable Directivity

A directional acoustical sensor with programmable axis of maximum sensitivity is described. The sensor is based on a combination of two orthogonal acoustical particle velocity (APV) sensors, integrated on the same chip. The APV sensors are based on a thermal transduction principle. Differently from former implementations, the proposed devices are fully CMOS compatible. Rotation of the sensitivity axis is obtained by combining the output of the two APV sensors properly weighted with programmable coefficients. This operation is performed using a microcontroller ADuC842 (Analog Devices) equipped with 12 bit, 400 kS ADCs.

Silicon Carbide Schottky Diodes for Alpha Particle Detection

The fabrication and characterization of SiC Schottky diodes for the detection of alpha particles at room temperature are described. A 5 × 5 matrix of diodes has been fabricated in order to verify the dependence of the device response on randomly distributed wafer defects. A dedicated exposure apparatus has been fabricated to test the detectors. Some preliminary alpha energy spectra obtained with the lowest reverse current diodes are shown.

A Compact Low-Offset Instrumentation Amplifier with Wide Input and Output Ranges

In this work, a new architecture for the design of very compact instrumentation amplifiers is proposed. The amplifier has been specifically developed for use as a versatile block for sensor interfacing. The most innovative feature of the proposed cell is the wide input common mode range, which has a margin to both power rails as small as 200 mV. The circuit, which has been implemented with the 3.3 V CMOS devices of the UMC 0.18 μm process, operates with supply voltage in the 1.4–3.6 V range. An input offset voltage standard deviation of 8 μV has been obtained using chopper modulation combined with gain enhancement of the output current mirrors. The amplifier performances are estimated by means of accurate electrical simulations.

Integrated Thermal Flow Sensors with Programmable Power-Sensitivity Trade-Off

A thermal flow sensor integrated with a programmable electronic interface into the same chip is proposed. The sensing structure is a micro-calorimeter with a double heater configuration fabricated with a simple post-processing technique applied to chip designed with a commercial CMOS process. The electronic interface is based on a low-noise, low-power instrumentation amplifier and a configurable heater current driver. The device characterization in nitrogen confirms the possibility to manage the trade-off between the sensitivity and the power delivered to the device by means of the programmable interface.

An Integrated Thermal Flow Sensor for Liquids Based on a Novel Technique for Electrical Insulation

A novel method to electrically insulate integrated thermal flow sensors from liquids is proposed. The sensor is fabricated with a post-processing technique applied to chips designed with a commercial CMOS process. A low cost packaging technique is used to convey the liquid to the sensing structures. After packaging, a simple technique is used to coat the flow channel and the chip area exposed to the fluid with silicone. Preliminary tests in water confirm the effectiveness of the proposed method.

Analysis of the response of innovative neutron detectors with monoenergetic neutron beams

Various neutron detectors are currently under development at the University of Pisa. The response of these devices is investigated using monoenergetic neutron beams produced at the CN accelerator of INFN Legnaro National Laboratories with thin lithium target bombarded by protons at different energies, exploiting the 7Li(p,n)7Be reaction.