1,720,961 research outputs found
Fully differential operational amplifier
No full textA fully differential operational amplifier is provided. The amplifier has input nodes and includes a differential input stage for receiving input signals over the input nodes and providing output signals on first and second intermediary nodes. The amplifier includes a fully differential amplification stage having positive and negative inputs coupled to the first and second intermediary nodes, respectively. The amplifier includes a first compensation transistor having conduction terminals coupled to the first intermediary node and a first node, and a control terminal coupled to a negative output of the fully differential amplification stage. The amplifier includes a second compensation transistor having conduction terminals coupled to the second intermediary node and a second node, and a control terminal coupled to a positive output of the fully differential amplification stage. The amplifier includes positive and negative output stages for providing amplifier outputs and feeding the outputs back to the amplifier
A Low-Power Sigma-Delta Modulator for Healthcare and Medical Diagnostic Applications
Full text linkThis paper presents a switched-capacitor Sigma-Delta modulator designed in 90-nm CMOS technology, operating at 1.2-V supply voltage. The modulator targets healthcare and medical diagnostic applications where the readout of small-bandwidth signals is required. The design of the proposed A/D converter was optimized to achieve the minimum power consumption and area. A remarkable performance improvement is obtained through the integration of a low-noise amplifier with modified Miller compensation and rail-to-rail output stage. The manuscript also presents a set of design equations, from the small-signal analysis of the amplifier, for an easy design of the modulator in different technology nodes. The Sigma-Delta converter achieves a measured 96-dB dynamic range, over a 250-Hz signal bandwidth, with an oversampling ratio of 500. The power consumption is 30 μW, with a silicon area of 0.39 mm2
Accurate Modeling of Ultra Low-Power Σ∆ Modulator
No full textThis paper presents a behavioural model suitable
for the simulation of low-power Sigma-Delta Modulators. Second-
order effects affecting the settling behaviour of the switched-
capacitor integrator was included, leading to improved accuracy.
Due to the oversampling mode of the converter, transistor-level
simulations are extremely time consuming. Accurate behavioural
models are thus mandatory in the first design phase of the
modulator, in particular when the involved analog blocks must
be optimized for minimum power consumption at some converter
resolution
An extended temperature range UHF RFID front-end in CMOS 350 nm
No full textThis paper describes the architecture and the transistor-level implementation of a UHF RFID front-end designed in CMOS 0.35μm technology with limited analog options to comply with EPC Class1/Generation2 standard. Since power acquisition is critical to RFID tag performance, two rectifier architectures are proposed and their performance is assessed by simulation in extended temperature range. In spite of technology constraints, good performance and low power consumption are obtained by the RFID front-end
Low-power 3rd order ΣΔ modulator in CMOS 90-nm for sensor interface applications
No full textThe manuscript describes the design and implementation of a low-power, fully differential switched-capacitor ΣΔ modulator in STM 90-nm CMOS technology, for sensor interface applications. With the aid of an accurate behavioral model, the power consumption is minimized without sacrificing the effective resolution. Through the optimization of single-stage integrators, with feed-forward summation, and using a class-A OTA op-amp with local positive feedback, a total power consumption of 50-μW from a 1.2-V power supply is achieved. The modulator reaches a peak SNR of 94-dB and a noise floor of 8.6-μV-rms over a 250-Hz signal bandwidth. The proposed design is one of the first modulator implemented in a 90-nm CMOS and achieving a 16-bit effective resolution with a 1.5-pJ/conv. figure-of-merit
Design Strategies and Modelling of Low-Power Sigma-Delta Analog-to-Digital Converters
No full textOggi, i dispositivi portatili sono diventati la forza trainante del mercato consumer e nuove sfide stanno emergendo per aumentarne le prestazioni, pur mantenendo un ragionevole tempo di vita della batteria.
Il dominio digitale è la miglior soluzione per realizzare funzioni di elaborazione del segnale, grazie alla scalabilità della tecnologia CMOS, che spinge verso l'integrazione a livello sub-micrometrico.
Infatti, la riduzione della tensione di alimentazione introduce limitazioni severe per raggiungere un range dinamico accettabile nel dominio analogico. Minori costi, minore consumo di potenza, maggiore resa e una maggiore riconfigurabilità sono i principali vantaggi dell'elaborazione dei segnali nel dominio digitale.
Da più di un decennio, diverse funzioni puramente analogiche sono state spostate nel dominio digitale.
Ciò significa che i convertitori analogico-digitali (ADC) stanno diventando i componenti chiave in molti sistemi elettronici. Essi sono, infatti, il ponte tra il mondo digitale e analogico e, di conseguenza, la loro efficienza e la precisione spesso determinano le prestazioni globali del sistema. I convertitori Sigma-Delta sono il blocco chiave come interfaccia in circuiti a segnale-misto ad elevata risoluzione e basso consumo di potenza. I tools di modellazione e simulazione sono strumenti efficaci ed essenziali nel flusso di progettazione.
Sebbene le simulazioni a livello transistor danno risultati più precisi ed accurati, questo metodo è estremamente lungo a causa della natura a sovracampionamento di questo tipo di convertitore.
Per questo motivo i modelli comportamentali di alto livello del modulatore sono essenziali per il progettista per realizzare simulazioni veloci che consentono di identificare le specifiche necessarie al convertitore per ottenere le prestazioni richieste.
Obiettivo di questa tesi è la modellazione del comportamento del modulatore Sigma-Delta, tenendo conto di diverse non idealità come le dinamiche dell'integratore e il suo rumore termico.
Risultati di simulazioni a livello transistor e dati sperimentali dimostrano che il modello proposto è preciso ed accurato rispetto alle simulazioni comportamentali.Today, portable devices have become the driving force of the consumer market and new challenges are emerging to increase the performance, while maintaining a reasonable battery life-time.
The digital domain is the best solution for implementing signal processing functions, thanks to the scaling of CMOS technology, which is pushing toward deep sub-micron integration level.
Indeed, the reduction of the voltage headroom introduces severe constraints for achieving an acceptable dynamic range in the analog domain. Lower cost, lower power consumption, higher yield, and higher reconfigurability are the major advantages of using digital signal processing.
Since more than a decade, several analog functions have been moved in the digital domain.
This evolution means that the analog-to-digital converters (ADCs) are becoming the key components in many electronic system. They are, indeed, the bridge between the analog and the digital worlds, and therefore, their efficiency and accuracy often determine the overall system performance. Sigma-Delta converters are the key block in high-resolution, and low-power mixed-signal interfaces. Efficient modelling and simulation tools are essential in the design flow.
Although transistor-level simulation is the most accurate approach, this method is extremely time consuming due to oversampling nature of this converter type.
For this reason high-level behavioural models of the modulator are mandatory for the designer in order to enable fast simulations and to identify the specifications leading to the required converter performance.
The focus of this thesis is on behavioural modelling of Sigma-Delta modulator, addressing several nonidealities such as the integrator's dynamics and thermal noise.
Results from transistor-level simulations and experimental data demonstrate the model to be valid and accurate when compared to behavioural simulations
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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