Dynamic Bias Research Articles

Power‐efficient class‐AB telescopic cascode opamp

A micropower telescopic cascode opamp is described. It employs an adaptive bias current source to obtain class-AB operation and dynamic biasing of the cascode transistors to improve output swing and common-mode rejection ratio (CMRR), and to avoid slew rate degradation. Measurement results for a 0.5 μm CMOS test chip prototype validate the proposal.

Navigation With Cellular CDMA Signals—Part II: Performance Analysis and Experimental Results

A framework for navigation using cellular code division multiple access (CDMA) signals is studied in this paper. Theoretical lower bounds on the navigation performance using pseudorange measurements drawn from the cellular CDMA base transceiver stations (BTSs) are derived. Moreover, the navigation performance for a mapper/navigator framework is studied in the presence of timing discrepancies between the mapper and navigator. In this framework, a mapping receiver (mapper) estimates the stochastic dynamic clock biases of the BTSs and shares these estimates with a navigating receiver (navigator). The optimal navigation performance of the mapper/navigator framework in the presence of timing discrepancies is analyzed, and a practical upper bound on the resulting position error is derived. Experimental results for a ground vehicle and unmanned aerial vehicles (UAVs) are presented. The ground vehicle results show a mean distance difference of 5.51 m between the cellular CDMA-only navigation solution and a GPS navigation solution in the absence of clock bias discrepancies. The UAV results show an improvement of 10.57 m in the root-mean-square error of the cellular CDMA navigation solution, when the sector clock bias discrepancies are accounted for utilizing the statistical model relating observed clock biases from different sectors of the same BTS cell.

How foreign direct investment affects CO2 emission levels in the Chinese manufacturing industry: Evidence from panel data

This study explores how inflows of foreign direct investment (FDI) affect a country’s carbon dioxide (CO2) emission levels. To investigate this relationship, we use panel data (2002–2015) from the 28 subsectors of the Chinese manufacturing sector. We also perform panel framework analysis to verify the characteristics of the panel data before establishing the panel estimator meant to test the relationships between carbon dioxide emissions, FDI inflows, industrial GDP, industry openness, net domestic fixed capital stock and cleaner production. The results of the panel framework analysis suggest the need to eliminate dynamic panel bias and produce more efficient and consistent parameter estimates. To do so, we use System Generalized Method of Moments (GMM) estimators with time dummies. Ultimately, the results of the analysis show that FDI is a positive predictor of environmental quality in the host country, which serves as evidence of the halo effect that FDI reduces CO2 emission levels. The study also finds evidence that industrial GDP and cleaner production improve environmental quality. However, the domestic capital stock has a negative effect on environmental quality. By showing that past carbon dioxide emissions significantly influence current emissions, our findings demonstrate the importance of consistency and persistence in efforts to reduce those emissions. Accordingly, we discuss some policy implications based on these results.

A 1.66 mV FOM Output Cap-Less LDO With Current-Reused Dynamic Biasing and 20 ns Settling Time

A fully integrated output capacitor-less, nMOS regulation FET low-dropout (LDO) regulator with fast transient response for system-on-chip power regulation applications is presented. The error amplifier (EA) consists of a differential cross-coupled common-gate (CG) input stage achieving twice the transconductance and unity-gain-bandwidth in comparison to a conventional differential common-source stage. The low input resistance of the CG EA improves stability of the LDO over a wide range of load currents. The LDO employs a current-reused dynamic biasing technique to further improve the load transient response, with no extra quiescent current. It is designed and fabricated in a 0.18- ${\mu }\text{m}$ CMOS technology for an input voltage range of 1.6–1.8 V, and an output voltage range of 1.4–1.6 V. Measured undershoot is 158 mV and settling time is 20 ns for 9–40 mA load change in 250 ps edge-time with zero load capacitance. The LDO core consumes 130 ${\mu }\text{A}$ of quiescent current, occupies 0.21 mm2 die area, and sustains 0–50 pF of on-chip load capacitance.

Ultralow-voltage albumen-gated electric-double-layer thin film transistors

In recent years, environment-friendly and biocompatible electronics have received extensive attention. As a kind of natural biological material with rich sources, proteins have been widely used in electronic devices. In this work, electric-double-layer (EDL) thin-film transistors (TFTs) gated by natural chicken albumen are fabricated at room temperature. The indium-tin-oxide (ITO) conductive glass is employed as a substrate. The spin coated chicken albumen film is used as the gate dielectric. The indium-zinc-oxide (IZO) is sputtered on an albumen-coated ITO glass as the channel and the source/drain electrodes with only one shadow mask. The capacitance-frequency measurements demonstrate an ultra-large specific capacitance of the albumen film at low frequencies. For the physical understanding of the capacitive coupling within the albumen film, the phase angle is characterized as a function of frequency. The results indicate that such an ultra-large capacitive coupling can be attributed to the proton migration under the electric field, which results in the EDL effect at the interface of the albumen film. By DC sweep measurements, a low leakage current is observed (<3.0 nA at <i>V</i><sub>gs</sub>=1.5 V), which indicates a good isolation of the albumen-based dielectric. By transfer and output measurements, an ultralow operation voltage of 1.5 V, a high field-effect mobility of 38.01 cm<sup>2</sup>/(V·s), a low subthreshold swing of 164 mV/decade, and a large on-off ratio of 2.4×10<sup>6</sup> are obtained for such albumen-gated TFTs. The ultra-large EDL capacitive coupling is responsible for such good electrical characteristics. The dynamic bias stress stability of the albumen-gated TFTs is also investigated. The device exhibits a good reproducibility in response to the repeatedly pulsed gate voltage. A maintainable on-to-off ratio (>10<sup>6</sup>) and no obvious current loss are observed, which suggests that neither chemical doping nor chemical reaction occurs at the albumen-based dielectric/IZO channel interface when the gate potential is biased. After being aged one day in air ambient without surface passivation, the albumen-gated TFTs show a good stability of the electrical properties. Such ultralow-voltage EDL-TFTs gated by albumen electrolyte will be useful for the bioelectronic and low-energy portable electronic products. And our results will also have potential applications in biocompatible artificial neuron networks and brain-inspired neuromorphic systems.

Quantitative Analysis of Situation Awareness (QASA): modelling and measuring situation awareness using signal detection theory

This paper presents a model of situation awareness (SA) that emphasises that SA is necessarily built using a subset of available information. A technique (Quantitative Analysis of Situation Awareness – QASA), based around signal detection theory, has been developed from this model that provides separate measures of actual SA (ASA) and perceived SA (PSA), together with a feature unique to QASA, a measure of bias (information acceptance). These measures allow the exploration of the relationship between actual SA, perceived SA and information acceptance. QASA can also be used for the measurement of dynamic ASA, PSA and bias. Example studies are presented and full details of the implementation of the QASA technique are provided.Practitioner Summary: This paper presents a new model of situation awareness (SA) together with an associated tool (Quantitative Analysis of Situation Awareness – QASA) that employs signal detection theory to measure several aspects of SA, including actual and perceived SA and information acceptance. Full details are given of the implementation of the tool.

Market structure in the Vietnamese banking system: a non-structural approach

PurposeThis paper aims to examine the market structure of Vietnam’s banking sector during 1999-2009, which is after the introduction of the two-tier banking system, using the non-structural (Panzar–Rosse) model.Design/methodology/approachThe authors consider a more comprehensive range of specifications, in terms of a greater number of environmental covariates and different dependent variables, than in the previous applications of this model. Further, this is the first study that uses lagged input prices (to avoid endogeneity), excludes assets (to avoid specification bias) and includes a lagged dependent variable (to avoid dynamic panel bias) in such a study of the Vietnamese banking system.FindingsThe authors find that the Vietnamese banking system operates in monopoly.Originality/valueThe main contribution of this paper is to determine the market structure in the recent period after the Vietnamese banking system was transformed into a less centralised, two-tier system. This study is the first to uniquely identify the market structure of this developing economy’s banking system (using data only for Vietnam and not observations from other countries) in a post-transition period.

Quantile Regression for Dynamic Panel Data Using Hausman–Taylor Instrumental Variables

This paper considers quantile regression for dynamic fixed effects panel data models with Hausman–Taylor instrumental variables (HTIV). The fixed effects estimators of panel data are typically biased when there existing lagged dependent variables and endogenous covariates as regressors, so we suggest the use of the Hausman–Taylor instrumental variables to reduce the dynamic bias. HTIV can be used even if independent variables do not vary with time when the unobserved heterogeneity is related to the independent variables. Besides, there is no need for HTIV to adapt instrumental variables beyond the model. In this paper, we consider Hausman–Taylor instrumental variables and propose two quantile regression estimators. We study the asymptotic properties of the proposed estimators. Monte Carlo simulation studies are conducted to examine the performance of the two proposed estimators. In addition, we illustrate the new approaches with an application to analyze the factors affecting price of commercialized residential buildings of 35 big and moderate cities in China, finding out that pre-price has a marked effect on current price.

A Prepulsing Technique for the Characterization of GaN Power Amplifiers With Dynamic Supply Under Controlled Thermal and Trapping States

The asymmetry between capture and release time constants associated with charge-trapping phenomena observed in the electrical characteristics of microwave gallium–nitride (GaN) field-effect transistors (FETs) introduces distortion in GaN-based power amplifiers (PA). The PAs that operate with supply modulation to increase efficiency are particularly affected by this phenomenon, since the GaN FET trap state exhibits a nonlinear dependence on the voltage applied to the device terminals. In this paper, a measurement approach and the setup are presented for a large-signal characterization of GaN-based PAs operated with dynamic bias supply: a new prepulsing technique is introduced, which enables the characterization of the PA in controlled charge-trapping and thermal states. The characteristics obtained with this technique are shown to give an accurate description of the PA performance in the actual application working conditions. The proposed approach is validated by using the measured data for the direct computation of predistortion functions for the linearization of a 9.7-GHz envelope tracking 10-W GaN monolithic microwave integrated circuit PA for amplitude-modulated pulsed radar transmitters. Additional research on the PA trap-induced performance degradation is also presented and can be explored to predict the PA performance for different parameters of the operative regime or for the formulation of the PA behavioral models.

A scalable open-source web-analytic framework to improve satellite-based operational water management in developing countries

Abstract Two software development hurdles to advancing real-world operationalization of satellite datasets for water management are addressed in this study. First, a simple, easy-to-build and open-source web portal connecting to a back-end complex model is developed for resource-constrained developing nations. Second, to enhance the skill of satellite-based predictions, an innovative and dynamic web analytics-based correction system is developed to reduce the uncertainty of satellite estimates. The correction system comprises dynamic precipitation bias correction and streamflow correction. Dynamically web crawled in-situ hydrologic data pertaining to the region are used to estimate satellite estimation bias. These corrected datasets are finally shared through the web portal. On average, these dynamic correction techniques reduced root mean squared error in streamflow by 80–90% for the case of South Asian river basins. The take-home message is that it is now possible to build cost-effective operational web portals based on satellite data and non-proprietary software.

A Switched-Capacitor Low-Pass Filter with Dynamic Switching Bias OP Amplifiers

A Switched-Capacitor Low-Pass Filter with Dynamic Switching Bias OP Amplifiers

INFLUENCE OF DYNAMIC MAGNETIZATION TO IMPROVE THE EFFICIENCY OF ELECTROMAGNETIC-ACOUSTIC TRANSFORMATION WITH WAVEGUIDE CONTROL RODS

The disadvantage of the electromagnetic-acoustic (EMA) method receiving ultrasonic waves are low efficiency. The traditional way to enhance its effectiveness is increase the bias field. The aim of the study was research the way to improve the efficiency of the EMA transformation, using a time-varying bias field.The researches held with the help of a specially designed installation that allows the magnetization to be performed by a constant and alternating magnetic field (dynamic bias), synchronously with the passage of the received pulse. The object of the study were rods made of different grades of steel with a diameter of 4–6 mm, in which the symmetrical zero mode S0 of the rod wave was excited by the EMA method (in the frequency range of about 40 kHz). A comparative analysis of the amplitudes and form pulses of multiple reflections during static and dynamic reversal of magnetization and with a full cycle of magnetization reversal conducted.The result of the efficiency measurements EMA reception during static and dynamic bias found a significant (up to 5 times) increase in the signal amplitude on the receiving transducer. Taking into account that the main contribution to the excitation mechanism and the reception mechanism made the magnetostrictive effect on low frecuncy, it can assumed that using a dynamic bias field is impacting significant on the effective mobility of magnetic domains (that is changes the dynamic magnetic susceptibility of the material). It is established that it is possible to monitor steel at lower values of the bias field, and, consequently, to reduce the mass dimensions of the magnetic system.Thus, in the course of the researchers found of effect of dynamic bias and effect of dynamic bias increase acoustic pulse amplitude of the signal of the received EMA method. Using this method will improve the quality EMA testing by creating more efficient EMA transducer. Taking into account that the value of the detected effect depends significantly on the steel grade, we can assume its possible application in the methods of express analysis, estimation of structural and stressed states.

Measurement and nonlinear behavioral modeling of the dynamic bias current in an LTE‐A Chireix PA

AbstractThe measurement and modeling of the dynamic power dissipation of a dual‐input Chireix power amplifier driven by LTE modulated signals is reported to optimize its dynamic efficiency. Two memory cubic spline FIR and NARMA behavioral models are verified to accurately predict the measured instantaneous PA bias‐current and power dissipation as a function of the PA RF output power.

Bayesian analysis of dynamic panel data by penalized quantile regression

Existing literature on quantile regression for panel data models with individual effects advocates the application of penalization to reduce the dynamic panel bias and increase the efficiency of the estimators. In this paper, we consider penalized quantile regression for dynamic panel data with random effects from a Bayesian perspective, where the penalty involves an adaptive Lasso shrinkage of the random effects. We also address the role of initial conditions in dynamic panel data models, emphasizing joint modeling of start-up and subsequent responses. For posterior inference, an efficient Gibbs sampler is developed to simulate the parameters from the posterior distributions. Through simulation studies and analysis of a real data set, we assess the performance of the proposed Bayesian method.

Low‐power three‐path inductor class‐C VCO without any dynamic bias circuit

A 2.48 GHz class-C voltage controlled oscillator (VCO) without any dynamic back bias circuit is presented. The VCO uses three-path high Q-factor inductor as the low loss resonator and class-C cross-coupled nMOSFET pairs for high dc/RF conversion efficiency and direct cross-coupled pMOSFET for dc current reuse. At the supply voltage of 1.2 V, the core power consumption is 0.24 mW. The phase noise of the VCO is −124 dBc/Hz and the VCO figure of merit is −197.0 dBc/Hz. The VCO was implemented in the TSMC standard 0.18 μm SiGe BiCMOS process and occupies a die area of 0.799 × 0.809 mm2.

A 6.6 mW 1.25–2.25 GHz low phase noise PLL frequency synthesizer based on wide tuning range Class-C VCO

A wide tuning range low phase noise phase-locked loop (PLL) frequency synthesizer based on Class-C voltage-controlled oscillator (VCO) for IEEE 802.11ah is presented. Feedback loop technique is adopted to provide dynamic gate bias to the core transistors of the Class-C VCO, guaranteeing robust start-up against process, voltage and temperature (PVT) variations. Automatic frequency control (AFC) algorithm with tail bias switching scheme is proposed to guarantee start-up condition and maintain optimum oscillation amplitude across the whole tuning range, avoiding the deterioration of figure-of-merit (FoM). Implemented in 65-nm CMOS, the presented frequency synthesizer prototype achieves a tuning range of 57%, from 1.25GHz to 2.25GHz. Drawing 5.5mA current from a 1.2-V power supply, the prototype demonstrates −127.8 dBc/Hz phase noise at 1-MHz offset and −94.6 dBc/Hz in-band phase noise from a carrier of 1.536GHz. With the proposed dynamic gate bias technique and AFC-assisted tail bias switching scheme, the wide tuning range Class-C VCO exhibits a peak FoM of 187.5 dBc/Hz, with only 2.5dB variation across the whole tuning range.

Effect of dynamic bias on accuracy of radioactive particle tracking (RPT) technique at different data acquisition frequencies

The accuracy of radioactive particle tracking technique depends on the ability to locate the exact position of a tracer particle. In the current work, experiments are performed to find the accuracy of an RPT measurement in terms of locating the position of the tracer particle and its velocity measurement. Results are presented for different tracer velocities at different data acquisition frequencies to minimize the error generated due to dynamic bias. Finally an optimal frequency is recommended for different velocities of a tracer particle to achieve the best possible accuracy.

Eye-Tracking Evidence of a Maintenance Bias in Social Anxiety.

The mechanisms and triggers of the attentional bias in social anxiety are not yet fully determined, and the modulating role of personality traits is being increasingly acknowledged. Our main purpose was to test whether social anxiety is associated with mechanisms of hypervigilance, avoidance (static biases), vigilance-avoidance or the maintenance of attention (dynamic biases). Our secondary goal was to explore the role of personality structure in shaping the attention bias. Participants with high vs low social anxiety and different personality structures viewed pairs of faces (free-viewing eye-tracking task) representing different emotions (anger, happiness and neutrality). Their eye movements were registered and analysed for both whole-trial (static) and time-dependent (dynamic) measures. Comparisons between participants with high and low social anxiety levels did not yield evidence of differences in eye-tracking measures for the whole trial (latency of first fixation, first fixation direction, total dwell time), but the two groups differed in the time course of overt attention during the trial (dwell time across three successive time segments): participants with high social anxiety were slower in disengaging their attention from happy faces. Similar results were obtained using a full-sample, regression-based analysis. Our results speak in favour of a maintenance bias in social anxiety. Preliminary results indicated that personality structure may not affect the maintenance (dynamic) bias of socially anxious individuals, although depressive personality structures may favour manifestations of a (static) hypervigilance bias.

A 2.24-mW, 61.8-dB SNDR, 20-MS/s Pipelined ADC With Charge-Pump-Based Dynamic Biasing for Power Reduction in Op Amp Sharing

A high-speed dynamic biasing technique is presented for reducing op amp power in discrete-time, multistage, analog circuits employing op amp sharing. To exploit typical power scaling in such circuits, a charge pump, of which the on-times of up and down currents are controlled by two comparators, performs rapid change of the op amp bias condition between a low-current mode and a high-current mode during nonoverlapping clock periods of the two phase clocks. The errors caused by finite comparator delay are compensated for by embedding intentional offset voltages in the comparators, which are implemented by using asymmetric differential input pairs in the comparators. To verify the efficacy of the proposed biasing technique, an 11-b pipelined analog-to-digital converter (ADC) has been implemented using 0.15-μm devices in a 28-nm CMOS technology. With a 20-MHz sampling clock, the ADC achieves a 61.8-dB SNDR while consuming a 2.24-mW power from a 1.8-V supply. The MDAC and ADC power are reduced by about 45% and 30%, respectively, compared with a conventional pipelined ADC employing an op amp in each MDAC. Owing to the simple structure of the proposed dynamic biasing, the prototype ADC occupies only 0.052 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Low‐phase noise Class‐C VCO with dynamic body bias

A 2.5 GHz Class-C voltage-controlled oscillator (VCO) with dynamic back-gate-biased MOSFET is proposed. A dynamic gate biasing circuit is used to reduce power consumption by switching N-type MOS from initial Class-AB to Class-C operation in steady state. Moreover, the VCO uses dynamic back-gate bias to reduce threshold voltage of switching MOSFET during the start-up oscillation. The Class-C differential VCO is implemented in TSMC 0.18 μm bipolar-complementary-metal-oxide-semiconductor (BiCMOS) process. The measured phase noise is -124.8 dBc/Hz at 1 MHz offset frequency from 2.48 GHz carrier while consuming 2.64 mW power from a 0.8 V supply. Tuning range of VCO is 0.72 GHz, from 2.48 to 3.3 GHz, whereas the control voltage was tuned from 0 to 2 V. The VCO occupies a chip area of 446 × 840 μm 2 and provides a figure of merit of -197.55 dBc/Hz.