Dc Bias Current Research Articles

A LOW POWER LOW PHASE NOISE LC VOLTAGE-CONTROLLED OSCILLATOR

A low phase noise CMOS complementary cross-coupled LC-tank voltage-controlled oscillator (VCO), implemented with TSMC 0.18μm 1P6M CMOS technology, is presented. Double pair pseudoresistance transistors biased by the tapped center of the inductor are utilized to reduce the DC bias current. The circuit consumes 1.55 mA from a 1.5 V supply voltage which saves up to 52.4% power, compared with the conventional one. Furthermore, an adaptive body biasing technique (ABB) is used to overcome the effect of PVT variations. The VCO is tunable from 2.58 to 3.07 GHz and has a phase noise −122.7 dBc/Hz at 1 MHz offset from the 3 GHz carrier. The Figure of Merit (FOM) of the proposed VCO is −188.8 dBc, and the figure of merit including the tuning range (FOMT ) is −193.5 dBc.

Gm-Realization of Controlled-Gain Current Follower Transconductance Amplifier

This paper describes the conception of the current follower transconductance amplifier (CFTA) with electronically and linearly current tunable. The newly modified element is realized based on the use of transconductance cells (G m s) as core circuits. The advantage of this element is that the current transfer ratios (i z/i p and i x/i z) can be tuned electronically and linearly by adjusting external DC bias currents. The circuit is designed and analyzed in 0.35 μm TSMC CMOS technology. Simulation results for the circuit with ±1.25 V supply voltages show that it consumes only 0.43 mw quiescent power with 70 MHz bandwidth. As an application example, a current-mode KHN biquad filter is designed and simulated.

I-shaped thermally actuated VHF resonators with submicron components

Thermally actuated piezoresistive readout single crystal silicon (SCS) resonators with a device footprint of ∼110μm2 have been experimentally demonstrated at operating frequencies of 112–176MHz. An SOIMEMS fabrication process was developed which incorporates electron beam lithography to achieve submicron dimensions. Demonstrated performance under vacuum (50–70Torr) includes a Q=5750 and motional conductance of 89.6μA/V. Frequency tunability of 2.1% in ambient and 3.66% under vacuum is achieved by variation of the DC bias current. The effects of asymmetry of the devices on operating frequency due to fabrication imperfections are considered qualitatively using commercial modeling software.

Thermal-Piezoresistive Energy Pumps in Micromechanical Resonant Structures

The internal thermoelectromechanical transduction loop in micromechanical resonant structures has been studied in this work and utilized to electronically enhance their quality factor or generate spontaneous mechanical vibrations. Electrothermal force generation in a micromechanical structure can be coupled to the structural stress through piezoresistive effect. Under certain conditions (specially having a negative piezoresistive coefficient in n-type crystalline silicon), this could allow mechanical vibrations of the structure to feed from a dc bias current applied to the structure, forming an electromechanical energy pump. At lower dc bias currents, the mechanical energy generated by the pump can only compensate a portion of the mechanical losses of the resonant structure, leading to self-Q-enhancement, whereas at higher currents, it can fully compensate all the mechanical losses, leading to self-sustained oscillation. Extensional-mode dual-plate resonators with frequencies as high as 18.1 MHz were fabricated, and quality factor amplification was successfully demonstrated for such. The ability of such resonators to initiate and maintain self-sustained oscillations under both vacuum and atmospheric pressures has also been demonstrated. Frequencies as high as 19.4 MHz, output voltage peak-to-peak amplitudes as high as 825 mV, and power consumptions as low as a few milliwatts have been demonstrated for such self-sustained oscillators.

Kinetic impedance and depairing in thin and narrow superconducting films

We use both Eilenberger-Usadel and Ginzburg-Landau (GL) theory to calculate the superfluid's temperature-dependent kinetic inductance for all currents up to the depairing current in thin and narrow superconducting films. The calculations apply to BCS weak-coupling superconductors with isotropic gaps and transport mean-free paths much less than the BCS coherence length. The kinetic inductance is calculated for the response to a small alternating current when the film is carrying a dc bias current. In the slow-experiment/fast-relaxation limit, in which the superconducting order parameter quasistatically follows the time-dependent current, the kinetic inductance diverges as the bias current approaches the depairing value. However, in the fast-experiment/slow-relaxiation limit, in which the the superconducting order parameter remains fixed at a value corresponding to the dc bias current, the kinetic inductance rises to a finite value at the depairing current. We then use time-dependent GL theory to calculate the kinetic impedance of the superfluid, which includes not only the kinetic reactance but also the kinetic resistance of the superfluid arising from dissipation due to order-parameter relaxation. The kinetic resistance is largest for angular frequencies $\omega$ obeying $\omega \tau_s > 1$, where $\tau_s$ is the order-parameter relaxation time, and for bias currents close to the depairing current. We also include the normal fluid's contribution to dissipation in deriving an expression for the total kinetic impedance. The Appendices contain many details about the temperature-dependent behavior of superconductors carrying current up to the depairing value.

Analysis and Research on Influence of Seam on Power Transformer's Capacity on Restraining DC Bias

Transformer is irreplaceable to make sure power system running stably. It's showed in research that magnetic resistance is relevant to capacity on restraining DC bias both in three-phase three-column transformer and three-phase five-column transformer. Magnetic resistance can be changed by changing the seam size of transformer. 3D field-circuit coupling models of single-phase four-column power transformer with two kinds of seam were created by FEA in this paper. Models were simulated with different DC bias current. The analysis result of influence of seam size on power transformer's capacity on restraining DC bias was obtained by DC bias current efficient extraction and comparison of models with different seam size, which is the theoretical basis of developing new transformer with more capacity on restraining DC bias.

Research on Vibration of Transformer with DC Bias

As the manufacturing technology of transformer getting more and more mature, issue of its vibration and noise is getting more and more attention. The vibration is more obviously when the transformer is running with DC Bias. 3D field-circuit coupling models of single-phase three-column power transformer was created by ANSYS. The simulating distributions of core magnetic flux density were obtained when the model was running with DC bias current of 0A, 0.9A and 2.6A. So were the modal shapes and curve of vibration-frequency of the transformer model. The theoretical guidance of reducing transformer vibration was obtained after analyzing the simulation result.

A Voltage Gain-Controlled Modified CFOA And Its Application in Electronically Tunable Four-Mode All-Pass Filter Design

This paper presents a new active building block (ABB) called voltage gain-controlled modified current feedback amplifier (VGC-MCFOA) based on bipolar junction transistor technology. The versatility of the new ABB is demonstrated in new first-order all-pass filter structure design employing single VGC-MCFOA, single grounded capacitor, and three resistors. Introduced circuit provides all four possible transfer functions at the same configuration, namely current-mode, transimpedance-mode, transadmittance-mode, and voltage-mode. The pole frequency of the circuit can be easily tuned by means of DC bias currents. The theoretical results are verified by SPICE simulations based on bipolar transistor arrays AT&T ALA400-CBIC-R process parameters.

Vibration and Audible Noise Characteristics of AC Transformer Caused by HVDC System Under Monopole Operation

When the HVDC system works in monopole ground return mode, dc current flows through the neutral of ac power transformer with the neutral grounded, which will enhance its vibration and audible noise. In this paper, dc bias experiments on ac power transformers carried out on 500-kV power transformers both in the transformer factory and the substation are described; the experimental results show how the vibration and audible noise of the transformer change under the dc bias current or windings voltage. The frequency characteristics of the vibration and audible noise of the dc-biased transformer are discussed under the conditions with and without loads. The direct connections between the vibration peak value and the dc bias current, and between the sound pressure and the dc bias current are revealed. Long-term online monitoring shows that the vibration of the transformer changes seriously even if there is not a dc system operating in monopole earth return mode, so when we analyze the influence of dc bias on the vibration and audible noise of the transformer, other influential factors should be expelled.

Generation and Modulation of a Millimeter-Wave Subcarrier on an Optical Frequency Generated via Optical Injection

A highly tunable millimeter-wave subcarrier signal is generated by optically injecting a Fabry-Perot semiconductor laser. The optically injected light, which enables microwave subcarrier frequencies well beyond the injected laser's free-running relaxation-oscillation frequency, is then on-off keyed by direct-current (dc) modulation of the injected slave laser. Adjustment of the subcarrier frequency is easily accomplished by changing either the dc bias current and/or junction temperature of the injected slave or the injecting master laser. In this paper, we theoretically and experimentally investigate the purity of the modulated microwave subcarrier. The generated microwave signal was then transmitted over 50 km of single-mode fiber, demonstrating the applicability of a directly modulated slave laser optically injected into the period-one state for radio-over-fiber applications.

GaN-Based Miniaturized Cyan Light-Emitting Diodes on a Patterned Sapphire Substrate With Improved Fiber Coupling for Very High-Speed Plastic Optical Fiber Communication

We demonstrate the performance of a novel cyan light-emitting diode (LED) on a patterned sapphire (PS) substrate as a light source for plastic optical fiber (POF) communications with the central wavelength at 500 nm. To further enhance the external quantum efficiency (EQE) and output power of this miniaturized high-speed LED, a LED with a PS substrate is adopted. Furthermore, by greatly reducing the number of active <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\hbox{In}_{\rm x}\hbox{Ga}_{1 - {\rm x}}\hbox{N/GaN}$</tex></formula> multiple quantum wells (MQWs) to four and minimizing the device active area, we can achieve a record-high electrical-to-optical (E–O) bandwidth (as high as 400 MHz) among all the reported high-speed visible LEDs under a very small dc bias current (40 mA). The fiber coupling efficiency has been improved in 4 dB using lens with a 500- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu \hbox{m}$</tex></formula> diameter mounted on the LED chip. Thus, the maximum fiber-coupled power was <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$-$</tex></formula> 2.67 dBm at the bias current of 40 mA. The 1.07-Gb/s data transmissions over a 50-m SI-POF fiber have been successfully demonstrated using this device at the bias current of 40 mA.

Calibration Enabled Scalable Current Sensor Module for Quiescent Current Testing

Semiconductor testing is aimed at screening fabrication defects that impact expected functionality. While catastrophic defects result in non working devices, parametric faults result in marginalities and are of increasing concern with deep sub-micron process technologies. This work presents a scheme to monitor Circuit-Under-Test (CUT) static bias current to identify catastrophic as well as parametric faults. All circuits require a deterministic amount of DC bias current which may vary outside the specifications when faults exist within the circuit. We propose a compensated current measurement Built-in-Current-Sensor (BICS) scheme, which can be used for sub-system level/circuit-level bias current measurements. The BICS provides accessibility to internal blocks and enables isolated parametric testing. Calibration routine enables process independence and provides robustness. The BICS is compatible with Very-Low-Cost Automatic Test Equipment (VLC-ATE), and can be used for detailed parametric testing in the production environment.

Serial Biasing of 16 Modular Circuits at 50 Gb/s

Rapid single-flux quantum circuits are generally biased in parallel with a common ground. As the integration scale increases, the total dc bias current can become too large to be practical. Applications such as large-scale Josephson-junction circuits for petaflops computers must avoid prohibitive dc bias requirements. Serial dc bias of multiple-circuit modules enables more efficient and effective operation of large circuits. This paper describes a circuit containing 1488 junctions in which the bias current was reused 16 times to reduce the required bias from ~100 mA to roughly 12 times less. We report initial results in which this circuit was operated up to 50 Gb/s with a negligible error rate.

Asymmetrical solutions and role of thermal fluctuations in dc current driven extended Josephson junction

Extended Josephson junction driven by dc bias current is studied numerically. Two types of solutions, symmetrical and asymmetrical, are found. The current–voltage characteristic (IVC) is calculated. The symmetrical solutions form main hysteretic IVC and asymmetrical ones create an additional branch. Depending on the bias current value periodic, quasiperiodic and chaotic modes of the junction motion was observed. Dynamics of the junction affected by thermal fluctuations was analyzed. Stability of different states of the junction is discussed.

Far-infrared electroluminescence characteristics of an Si-based photodiode under a forward DC bias current

At room temperature, the bias dependence of a far-infrared electroluminescence image of a photodiode is investigated in the dark condition. The results show that the electroluminescence image can be used to detect defects in the photodiode. Additionally, it is found that the electroluminescence intensity has a power law dependence on the dc bias current. The photodiode ideality factor could be obtained by a fitting a relationship between the electroluminescence intensity and the bias current. The device defect levels will be easily determined according to the infrared image and the extracted ideality factor value. This work is of guiding significance for current solar cell testing and research.

Heavy metallic oxide nanoparticles for enhanced sensitivity in semiconducting polymer x-ray detectors

Semiconducting polymers have previously been used as the transduction material in x-ray dosimeters, but these devices have a rather low detection sensitivity because of the low x-ray attenuation efficiency of the organic active layer. Here, we demonstrate a way to overcome this limitation through the introduction of high density nanoparticles having a high atomic number (Z) to increase the x-ray attenuation. Specifically, bismuth oxide (Bi2O3) nanoparticles (Z = 83 for Bi) are added to a poly(triarylamine) (PTAA) semiconducting polymer in the active layer of an x-ray detector. Scanning electron microscopy (SEM) reveals that the Bi2O3 nanoparticles are reasonably distributed in the PTAA active layer. The reverse bias dc current–voltage characteristics for PTAA–Bi2O3 diodes (with indium tin oxide (ITO) and Al contacts) have similar leakage currents to ITO/PTAA/Al diodes. Upon irradiation with 17.5 keV x-ray beams, a PTAA device containing 60 wt% Bi2O3 nanoparticles demonstrates a sensitivity increase of approximately 2.5 times compared to the plain PTAA sensor. These results indicate that the addition of high-Z nanoparticles improves the performance of the dosimeters by increasing the x-ray stopping power of the active volume of the diode. Because the Bi2O3 has a high density, it can be used very efficiently, achieving a high weight fraction with a low volume fraction of nanoparticles. The mechanical flexibility of the polymer is not sacrificed when the inorganic nanoparticles are incorporated.

Surface Multi-Purposes Low Power Wireless Electromyography (EMG) system Design

The progress in the field of electronics and technology as well as the processing of signals coupled with advance in the use of computer technology has given the opportunity to record and analyze the bio-electric signals from the human body in real time that requires dealing with many challenges according to the nature of the signal and its frequency. This could be up to 1 kHz, in addition to the need to transfer data from more than one channel at the same time. Moreover, another challenge is a high sensitivity and low noise measurements of the acquired bio-electric signals which may be tens of micro volts in amplitude. For these reasons, a low power wireless Electromyography (EMG) data transfer system is designed in order to meet these challenging demands. In this work, we are able to develop an EMG analogue signal processing hardware, along with computer based supporting software. In the development of the EMG analogue signal processing hardware, many important issues have been addressed. Some of these issues include noise and artifact problems, as well as the bias DC current. The computer based software enables the user to analyze the collected EMG data and plot them on graphs for visual decision making. The work accomplished in this study enables users to use the surface EMG device for recording EMG signals for various purposes in movement analysis in medical diagnosis, rehabilitation sports medicine and ergonomics. Results revealed that the proposed system transmit and receive the signal without any losing in the information of signals.

Spin-transfer-torque switching in spin valve structures with perpendicular, canted, and in-plane magnetic anisotropies

We exploit canted anisotropies as possible means to enhance spin-transfer-torque (STT) and reduce switching currents. The STTs in spin-valve structures with perpendicular, canted, and, as a reference, in-plane magnetic anisotropies were studied. For perpendicular magnetic anisotropy and canted spin valves the thicknesses and number of Co and Pt layers were varied to obtain different angles of the magnetic anisotropy with respect to the sample plane. Point contact measurements were used to measure the change in the switching-field of the magnetization with the change in the bias current applied to the point contact. A larger STT effect, as evidenced by a larger change in the switching magnetic field for the unit change in the dc bias current, was observed for the sample with 45∘ tilt in magnetization compared to a sample with 12∘ tilt. Tilted magnetization of the reference layer causes precessional switching, decreasing the switching energy and time. Micromagnetic simulations were performed to explain the experimental observations.

Design and Performance of a Bidirectional Isolated DC–DC Converter for a Battery Energy Storage System

This paper describes the design and performance of a 6-kW, full-bridge, bidirectional isolated dc-dc converter using a 20-kHz transformer for a 53.2-V, 2-kWh lithium-ion (Li-ion) battery energy storage system. The dc voltage at the high-voltage side is controlled from 305 to 355 V, as the battery voltage at the low-voltage side (LVS) varies from 50 to 59 V. The maximal efficiency of the dc-dc converter is measured to be 96.0% during battery charging, and 96.9% during battery discharging. Moreover, this paper analyzes the effect of unavoidable dc-bias currents on the magnetic-flux saturation of the transformer. Finally, it provides the dc-dc converter loss breakdown with more focus on the LVS converter.

Operation of YBCO Current Leads as Bias Lines to Cryocooler-mounted 4K Superconducting Electronics

Abstract We report on the construction and operation of flexible, 15-line YBCO lead assemblies as low heat-leak bias lines to a complex Rapid Single Flux Quantum (RSFQ) circuit on a 2-stage cryocooler. The leads are used to supply DC bias currents of about 30 mA per line to the circuitry operating at 4 K. They span the temperature difference between the 1st (∼50 K) and 2nd (∼4 K) stages of a Gifford-McMahon cryocooler, substantially cutting the heat load to the 2nd stage when compared to optimized normal metal leads. No measurable change in the temperature of the 4 K stage associated in Joule heating in the superconducting leads or end joints was observed when the full set of 24 bias lines was taken to operational current, and no degradation was observed after the cryocooler maintained temperature for six months. The leads are made by patterning 12 mm-wide 2G tape, the heat load of which is dominated by conduction through the cable's Hastelloy substrate. We have measured the thermal and electrical transport properties of the Hastelloy® substrate and believe that they are significantly changed by processing history.