Tales Cleber Pimenta

An Ultra-Low-Voltage Ultra-Low-Power CMOS Miller OTA With Rail-to-Rail Input/Output Swing

An ultra-low-voltage ultra-low-power CMOS Miller operational transconductance amplifier (OTA) with rail-to-rail input/output swing is presented. The topology is based on combining bulk-driven differential pair and dc level shifters, with the transistors work in weak inversion. The improved Miller OTA has been successfully verified in a standard 0.35-mum CMOS process. Experimental results have confirmed that, at a minimum supply voltage of 600 mV, lower than the threshold voltage, the topology presents almost rail-to-rail input and output swings and consumes only 550 nW.

A Low Power CMOS Voltage Regulator for a Wireless Blood Pressure Biosensor

This paper describes a CMOS implementation of a linear voltage regulator (LVR) used to power up implanted physiological signal systems, as it is the case of a wireless blood pressure biosensor. The topology is based on a classical structure of a linear low-dropout regulator. The circuit is powered up from an RF link, thus characterizing a passive radio frequency identification (RFID) tag. The LVR was designed to meet important features such as low power consumption and small silicon area, without the need for any external discrete components. The low power operation represents an essential condition to avoid a high-energy RF link, thus minimizing the transmitted power and therefore minimizing the thermal effects on the patients tissues. The project was implemented in a 0.35-μm CMOS process, and the prototypes were tested to validate the overall performance. The LVR output is regulated at 1 V and supplies a maximum load current of 0.5 mA at 37°C. The load regulation is 13 mV/mA, and the line regulation is 39 mV/V. The LVR total power consumption is 1.2 mW.

A CMOS threshold voltage reference source for very-low-voltage applications

This paper describes a CMOS voltage reference that makes use of weak inversion CMOS transistors and linear resistors, without the need for bipolar transistors. Its operation is analogous to the bandgap reference voltage, but the reference voltage is based on the threshold voltage of an nMOS transistor. The circuit implemented using 0.35@mm n-well CMOS TSMC process generates a reference of 741mV under just 390nW for a power supply of only 950mV. The circuit presented a variation of 39ppm/^oC (after individual resistor trimming) for the -20 to +80^oC temperature range, and produced a line regulation of 25mV/V for a power supply of up to 3V.

A heart disease recognition embedded system with fuzzy cluster algorithm

This article presents the viability analysis and the development of heart disease identification embedded system. It offers a time reduction on electrocardiogram - ECG signal processing by reducing the amount of data samples, without any significant loss. The goal of the developed system is the analysis of heart signals. The ECG signals are applied into the system that performs an initial filtering, and then uses a Gustafson-Kessel fuzzy clustering algorithm for the signal classification and correlation. The classification indicated common heart diseases such as angina, myocardial infarction and coronary artery diseases. The system uses the European electrocardiogram ST-T Database (EDB) as a reference for tests and evaluation. The results prove the system can perform the heart disease detection on a data set reduced from 213 to just 20 samples, thus providing a reduction to just 9.4% of the original set, while maintaining the same effectiveness. This system is validated in a Xilinx Spartan(®)-3A FPGA. The field programmable gate array (FPGA) implemented a Xilinx Microblaze(®) Soft-Core Processor running at a 50MHz clock rate.

An Ultra Low-Voltage Ultra Low-Power CMOS Threshold Voltage Reference

This paper describes a CMOS voltage reference that makes use of weak inversion CMOS transistors and linear resistors, without the need for bipolar transistors. Its operation is analogous to the bandgap reference voltage, but the reference voltage is based on the threshold voltage of an nMOS transistor. The circuit implemented using 0.35 μm n-well CMOS TSMC process generates a reference of 741 mV under just 390 nW for a power supply of only 950 mV. The circuit presented a variation of 39 ppm/°C for the -20°C to +80°C temperature range, and produced a line regulation of 25 mV/V for a power supply of up to 3 V.

A CMOS low-voltage low-power temperature sensor

Temperature sensing circuits are used in a wide range of applications such as in the biomedical area, cold chain monitoring and industrial applications. In the biomedical area, temperature patient monitoring systems can be found in a wide range of hospital applications such as the intensive care unit, surgery rooms and clinical analysis. When the systems also incorporate also communication features, they form a telemedicine system in which the patients can be remotely monitored. The need of portability promotes a demand for sensors and signal conditioners that can be placed directly on the patient or even implanted. Implanted systems provide comfort for the patient during the physiologic data acquisition. These systems should operate preferably without a battery, in which the energy is obtained by inductive coupling (RF link). Implanted devices require low-voltage and low-power operation in a small silicon area in order to offer safety to the patient, mainly in terms of excessive exposure to RF. This work presents a low-voltage low-power temperature sensor, suitable for implanted devices. The circuit topology is based on the composite transistors operating in weak inversion, requiring extremely low current, at low-voltage (0.8V), with just 100nW power dissipation. The circuit is very simple and its implementation requires a small silicon area (0.062mm^2). The tests conducted in the prototypes validate the circuit operation.

An Ultra-Low-Voltage Ultra-Low-Power Weak Inversion Composite MOS Transistor : Concept and Applications

This work presents an ultra-low-voltage ultra-low-power weak inversion composite MOS transistor. The steady state power consumption and the linear swing signal of the composite transistor are comparable to a single transistor, whereas presenting very high output impedance. This work also presents two interesting applications for the composite transistor; a 1:1 current mirror and an extremely low power temperature sensor, a thermistor. Both implementations are verified in a standard 0.35-μm TSMC CMOS process. The current mirror presents high output impedance, comparable to the cascode configuration, which is highly desirable to improve gain and PSRR of amplifiers circuits, and mirroring relation in current mirrors.

A low-voltage low-power CMOS V-I converter with rail-to-rail differential input for filtering applications

A low-voltage (/spl les/3 V) low-power CMOS voltage-to-current converter is introduced which has an almost rail-to-rail differential-input swing (/spl plusmn/1.5 V) with a low signal-distortion (/spl les/1%) with a minimum supply voltage of 2 V. The proposed circuit uses class-AB linearization to achieve full-input-swing in the saturation region. In a 1.2 /spl mu/m n-well CMOS process, the 3 dB frequency of the V-I converter is in the range of 113-114 MHz with different biases. The total power consumption is around 0.7 mW. A simple fully-differential 5th-order elliptic filter composed of the proposed V-I converters has THD below 1% with peak-to-peak V/sub out/=1.2 V.

Photovoltaic Array Reconfiguration Strategy for Maximization of Energy Production

This paper presents a dynamic reconfiguration method for electrical connections in a Series-Parallel connected photovoltaic array under partial shading conditions. It is desirable to extract the maximum energy from the array, but it does not occur in situations where the modules have different points of operation caused by shading. The proposed method is then characterized by the maintenance of the PV array dimensions, that is; no module is removed or added to the array. Furthermore, the control algorithm is based on the Rough Sets Theory, which allows the fast and efficient implementation of a control system, comprising rules that identify the system optimal configuration.

Low power low noise bio-amplifier with adjustable gain for digital bio-signals acquisition systems

This work describes a symmetrical power supplied (±1.8 V) 0.5 μm CMOS implementation of a bio-amplifier designed for use in digital acquisition systems. The whole acquisition system under fabrication will still contain a 3rd order switched capacitor anti-alias eliptic filter, a sample and hold, an ADC and a SPI interface. In this paper though the focus is over the analog circuitry responsable of amplifing the bio-signals. The achievable gains are controlled through a switched capacitor technique and can achieve over 70 dB with 2.5 μVRMS of input referred noise within 1.5 kHz bandwith. The circuit dissipates 33.2 μW in 0.192 mm2.