Showing papers on "Capacitor published in 1995"

Multilevel converters-a new breed of power converters

Abstract: Multilevel voltage source converters are emerging as a new breed of power converter options for high-power applications. The multilevel voltage source converters typically synthesize the staircase voltage wave from several levels of DC capacitor voltages. One of the major limitations of the multilevel converters is the voltage unbalance between different levels. The techniques to balance the voltage between different levels normally involve voltage clamping or capacitor charge control. There are several ways of implementing voltage balance in multilevel converters. Without considering the traditional magnetic coupled converters, this paper presents three recently developed multilevel voltage source converters: (1) diode-clamp, (2) flying-capacitors, and (3) cascaded-inverters with separate DC sources. The operating principle, features, constraints, and potential applications of these converters are discussed.

Fatigue-free ferroelectric capacitors with platinum electrodes

Abstract: A SIGNIFICANT fraction of the computer memory industry is at present involved in the manufacture of non-volatile memory devices1—that is, devices which retain information when power is interrupted. For such applications (and also for volatile memories), the use of capacitors constructed from ferroelectric thin films has stimulated much interest1. In such structures, information is stored in the polarization state of the ferroelectric material itself, which should in principle lead to lower power requirements, faster access time and potentially lower cost1. But the use of ferroelectrics is not without problems; the memories constructed to date have generally suffered from poor retention of stored information and degradation of performance ('fatigue') with use1–3. Here we describe the preparation and characterization of thin-film capacitors using ferroelectric materials from a large family of layered perovskite oxides, exemplified by SrBi2Ta2O9, SrBi2NbTaO9 and SrBi4Ta4O15. The structural flexibility of these materials allows their properties to be tailored so that many of the problems associated with previous ferroelectric memories are avoided. In particular, our capacitors do not show significant fatigue after 1012 switching cycles, and they exhibit good retention characteristics and low leakage currents even with films less than 100 nm thick.

Dielectric Materials and Applications

Abstract: Theory dielectric measuring techniques dielectric materials and their applications - dielectric materials insulation strengths of high pressure gases and of vacuum liquid dielectrics plastics as dielectrics ceramics dielectrics in equipment dielectrics in power and distribution equipment dielectrics in electronic equipment dielectrics in capacitors rubber and plastics in cables problems of the cable engineer dielectric materials as devices rectifiers piezoelectric transducers and resonators magnetic and dielectric amplifiers memory devices dielectric requirements of the armed forces tables of dielectric materials

A three-phase power flow method for real-time distribution system analysis

Abstract: This paper presents a three-phase power flow solution method for real-time analysis of primary distribution systems. This method is a direct extension of the compensation-based power flow method for weakly meshed distribution systems from single phase to three-phase, with the emphasis on modeling of dispersed generation (PV nodes), unbalanced and distributed loads, and voltage regulators and shunt capacitors with automatic local tap controls. The method proposed here is capable of addressing these modeling challenges while still maintaining a high execution speed required for real-time application in distribution automation systems. The paper also includes test results from the application of a computer program developed based on the proposed method to large primary electric distribution systems. >

A New Charge Storage Mechanism for Electrochemical Capacitors

Abstract: The hydrous form of ruthenium oxide (RuO[sub 2][center dot]xH[sub 2]O) has been demonstrated to be an excellent electrode material for electrochemical capacitors. This material, as prepared by a sol-gel process at low temperatures, is amorphous and electrically conductive. The specific capacitance is over 720 F/g. This value is at least two times higher than the highest value ever reported for such materials. The charge storage mechanism is believed to involve bulk electrochemical protonation of the oxide. This discovery opens a new avenue of research in the field of high energy density electrochemical capacitors.

A 10 b, 20 Msample/s, 35 mW pipeline A/D converter

Abstract: ―This paper describes a 10 b, 20 Msample/s pipeline A/D converter implemented in 1.2 μm CMOS technology which achieves a power dissipation of 35 mW at full speed operation. Circuit techniques used to achieve this level of power dissipation include digital correction to allow the use of dynamic comparators, and optimum scaling of capacitor values through the pipeline. Also, to be compatible with low voltage mixed-signal system environments, a switched capacitor (SC) circuit in each pipeline stage is implemented and operated at 3.3 V with a new high-speed, low-voltage operational amplifier and charge pump circuits. Measured performance includes 0.6 LSB of INL, 59.1 dB of SNDR (Signal-to-Noise-plus-Distortion-Ratio) for 100 kHz input at 20 Msample/s. At Nyquist sampling (10 MHz input), SNDR is 55.0 dB. Differential input range is ± 1 V, and measured input referred RMS noise is 220 μV. The power dissipation at 1 MS/s is below 3 mW with 58 dB of SNDR.

Performance limits of switched-capacitor DC-DC converters

Abstract: The theoretical performance limits of two-phase switched-capacitor (SC) DC-DC power converters are discussed in this paper. For a given number of capacitors k, the complete set of attainable DC conversion ratios is found. The maximum step-up or step-down ratio is given by the k/sup th/ Fibonacci number, while the bound on the number of switches required in any SC circuit is 3k-2. Practical implications, illustrated by several SC power converter examples, include savings in the number of components required for a given application, and the ability to construct SC power converters that can maintain the output voltage regulation and high conversion efficiency over a wide range of input voltage variations. Limits found for the output resistance and efficiency can be used for selection and comparison of SC power converters. >

Capacitor structure for an integrated circuit

Abstract: A capacitor structure for an integrated circuit and a method of fabrication are described. The capacitor structure is defined by layers forming interconnect metallization and interlayer dielectrics. The latter are relatively thick, and provide high breakdown voltages. Multilevel metallization schemes allow for a stack of a plurality of electrodes to be provided. The electrodes may take the form of stacks of flat plates interconnected in parallel so that the capacitance is the sum of capacitances of alternate layers in the stack. Advantageously each electrode comprises a main portion and a surrounding portion having the form of a protecting ring, coplanar with the main portion of the electrode. The ring prevents thinning of the dielectric near edges of electrode during fabrication, to improve control of breakdown voltages for high voltage applications. Alternative electrode structures employing a plurality of interconnected fingers, and particularly a configuration having interdigitated fingers, are provided to increase the capacitance per unit surface area. Parallel electrode fingers are stacked in vertical alignment, or offset, and interconnected to provide vertical, horizontal or inclined stacks having different patterns of polarities, thereby forming capacitors of various configurations. The capacitor structures have particular application for high voltage (>100 V), low leakage and high frequency (MHz/GHz) applications.

Apparatus for monitoring power of battery to supply electric power to load

Abstract: A micro discharge detection current which is obtained by reducing a discharge current of a battery at a predetermined ratio is detected by a current amplifying circuit and an integration voltage showing a discharge charge amount is formed by charging a capacitor of an integrating circuit. The integration voltage of the integrating circuit is compared with a reference voltage showing a predetermined unit charge amount by a comparing circuit. When the integration voltage reaches the reference voltage, a comparison output is inverted and the capacitor of the integrating circuit is discharge reset and one pulse signal showing the unit charge amount is generated by the inversion of the comparison output. The pulse signal from the comparing circuit is counted by a counter and the count value is multiplied with the unit charge amount, thereby obtaining the present discharge charge amount of the battery.

Current controlled bandpass filter based on translinear conveyors

Abstract: A new concept to take advantage of the parasitic resistance that appears on port X of the second-generation current conveyors is introduced. This parasitic resistance, which is controllable in current, leads to the definition of the second generation current controlled conveyors (CCCII). A current controlled bandpass filter, operating in the current mode, is also described. It uses only two CCCII+s and two capacitors. Its central frequency can be adjusted by acting on the bias current of the conveyors. SPICE simulation results, in agreement with theory, are given for central frequencies around 30 MHz.

Pulsed laser ablation synthesis and characterization of layered pt/srbi2ta2o9/pt ferroelectric capacitors with practically no polarization fatigue

Abstract: Pulsed laser ablation deposition was used to synthesize polycrystalline SrBi2Ta2O9 layered ferroelectric thin films on platinized silicon substrates. Top electrodes were produced by dc magnetron sputter deposition to fabricate capacitors for electrical tests. The polarization electric field hysteresis loops showed saturation in the 2–4 V range with a coercive field of 25 kV/cm. The capacitors showed practically no polarization fatigue up to 1011 switching cycles. The resistivity of the SrBi2Ta2O9 for a coercive field of 100 kV/cm was approximately 2×1011 Ω cm. Retention and imprint characteristics of these capacitors showed no degradation as a function of cumulative waiting times.

Modeling and analysis of multichip module power supply planes

Abstract: A method that would allow accurate modeling of arbitrarily shaped planes with bypass capacitors has been developed. It is compatible with a SPICE-based modeling method for the rest of the power supply hierarchy and the devices. A modified SPICE is used to accommodate distributed circuits. The distributed circuits are built with microwave analysis software and connected to SPICE by s-parameter files. The modeling process is described and examples of thick and thin-film power supply planes are presented with comparison to measured results. The method is used to explore potential design choices for a large MCM with many simultaneously switching drivers. >

Filtered feedthrough assembly having a mounted chip capacitor for medical implantable devices and method of manufacture therefor

Abstract: A filtered feedthrough assembly (100, 100', 100", 200, 200", 300) for use in implantable medical devices is provided. The filtered feedthrough assembly provides at least one chip capacitor (110, 210) or an LC circuit coupled between a lead wire (12) and an end surface (18) of a metallic ferrule (14). The chip capacitor is secured in position by means of a [non-conductive film (122) and] conductive material (120) applied to opposing ends of the chip capacitor. The end portion of the feedthrough and chip capacitor may be encapsulated by an encapsulant (102) to provide a moisture resistant coating therefor.

Implantable medical device having shielded and filtered feedthrough assembly and methods for making such assembly

Abstract: A wireless feedthrough assembly, for coupling leads received in the receptacles of a connector assembly to the electronic circuit within a cardiac pacemaker, includes a weld ring mounted in hermetically sealed fashion within a housing wall of the pacemaker and itself hermetically sealed to an intermediate portion of an elongated, multilayered structure. The multilayered structure includes layers of electrically insulating ceramic material on opposite sides of a planar array of printed conductors extending between a first portion of the structure within the connector assembly and an opposite second portion of the structure within the pacemaker. Connector pads at the ends of the printed conductors within the first portion are coupled to the receptacles of the connector assembly, while contact pads at the exterior of the second portion and coupled by vias to connector pads at the ends of the printed conductors are coupled to the electronic circuits within the pacemaker. Printed ground planes on the multilayered structure form a conductive envelope which shields the printed conductors from electric fields. The contact pads include positive and ground contacts to which are coupled discrete filtering capacitors for limiting the spectrum of frequencies receivable by the connector assembly. A method for making the aforedescribed feedthrough assembly is also disclosed.

Power bus decoupling on multilayer printed circuit boards

Abstract: Guidelines for the selection and placement of decoupling capacitors that work well for one-sided or two-sided printed circuit boards are not appropriate for multilayer boards with power and ground planes. Boards without internal planes take advantage of the power bus inductance to help decouple components at the higher frequencies. An effective decoupling strategy for multilayer boards must account for the low inductance and relatively high capacitance of the power bus. >

Voltage shifts and imprint in ferroelectric capacitors

Abstract: Voltage offsets in the polarization‐voltage characteristics of Pb(Zr,Ti)O3 capacitors can be induced by either thermal or optical processes. The thermally (optically) induced voltage shift occurs by heating (illuminating) the sample under remanence or a saturating bias. Generally speaking, the thermally induced voltage shifts are greater than those obtained optically; this is attributed to the role of oxygen vacancy‐related defect dipoles throughout the film. We find that the inclusion of a dopant element that occupies a portion of the Ti(Zr) sites and has an oxidation state greater than +4 reduces the thermally induced voltage shifts observed in the capacitors. This may result because these particular dopants reduce the oxygen vacancy density and, hence, the defect‐dipole contribution to the voltage shift.

Characteristics of Bismuth Layered SrBi2Ta2O9 Thin-Film Capacitors and Comparison with Pb(Zr, Ti)O3

Abstract: We have developed the series of thin-film bismuth layer structured ferroelectric (BLSF) materials such as SrBi2Ta2O9, SrBi2Nb2O9, SrBi4Ti4O15 and their solid solutions using metallo-organic-decomposition (MOD) spin-on coating techniques. We found that SrBi2Ta2O9 is one of the best potential candidate materials for ferroelectric nonvolatile memories. The SrBi2Ta2O9 thin-film capacitor had the remanent polarization (P r+-P r-) of 20 µ C/cm2, coercive field of 35 kV/cm and dielectric constant of 250. SrBi2Ta2O9 thin film on platinum electrode has fatigue-free characteristics for up to 2×1011 cycles without requiring any complicated electrode system such as conductive oxide. Moreover, SrBi2Ta2O9 thin film has many advantages, e.g., high signal/noise ratio of 8 at 1.2 V, low-voltage operation at as low as 1 V, long data-retention, little surface effect, superior imprint properties and low leakage current. We considered that these advantages are due to (1) less space charge and (2) the inherent domain motion.

Cmos integrated microsensor with a precision measurement circuit

Abstract: Improved microsensors are provided by combining surface micromachined substrates, including integrated CMOS circuitry, together with bulk micromachined wafer bonded substrates which include at least part of a microelectromechanical sensing element. In the case of an accelerometer, the proof mass is included within the wafer bonded bulk machined substrate, which is bonded to the CMOS surface machine substrate, which has corresponding etch pits defined therein over which the wafer bonded substrate is disposed, and in the case of accelerometer, the proof mass or thin film membranes in the case of other types of detectors such as acoustical detectors or infrared detectors. A differential sensor electrode is suspended over the etch pits so that the parasitic capacitance of the substrate is removed from the capacitance sensor, or in the case of a infrared sensor, to provide a low thermal conductance cavity under the pyroelectric refractory thin film. Where a membrane suspended electrode is utilized over an etch pit, one or more apertures are defined therethrough to avoid squeeze film damping. Accelerometers built according to the methodology are provided with a nulling feedback voltage to maintain the switch DC voltage across sensing capacitors in a null condition and to maintain high sensitivity without requiring either a precision transformer or regulated power sources in the capacitance bridge of the accelerometer.

High speed crystallography detector

Abstract: A device for the collection, digitization and analysis of synchrotron x-ray crystallographic data using an area detector which detects x-ray photons directly on arrays of solid state detectors and stores the information on capacitors located on readout unit cell array chips. The device consists of a two dimensional area detector, for amplification, collection and conversion of the diffracted x-rays to electrical signals, drive electronics for providing the timing pulses and biases to the area sensor, output electronics for converting the x-ray signals to digital signals and storing the signals, and a data processor to analyze the digital signal form the output electronics. The solid-state detector array is made up of a variable-area three-dimensional array of detector array chips where each chip is in turn made up of an array of solid-state detectors. Each detector on the detector array chip is electrically connected to a readout unit cell on a readout array chip directly beneath the detector array chip. The readout unit cell contains the circuitry for storage, switching and readout of the x-ray signals.

Process of fabricating dynamic random access memory device having storage capacitor low in contact resistance and small in leakage current through tantalum oxide film

Abstract: When tantalum oxide is used for a dielectric film of a stacked type storage capacitor forming a memory cell together with a switching transistor, heat treatments are limited to 530 degrees centigrade in the stages after the deposition of the tantalum oxide, and leakage current across the tantalum oxide is drastically decreased.

Airbag application: a microsystem including a silicon capacitive accelerometer, CMOS switched capacitor electronics and true self-test capability

Abstract: A low cost, high reliability accelerometer microsystem designed for crash sensing in automotive airbag electronic control units is presented. The proposed microsystem offers high level output, on-line self-test function, small size (3.5 mm × 3.5 mm × 1.15 mm), and high design flexibility thanks to a two-chip construction. The sensitive part is a surface micromachined capacitive interdigitated structure realized from a SIMOX SOI substrate. The accelerometer operates in a closed loop mode using electrostatic feedback with conditioning circuitry realized in a 2 μm CMOS process. A high performance readout circuit using switched capacitors has been developed. Behavioural simulation results show a bandwidth of 630 Hz at ±50 g with 5 V power supply. The fabrication process includes the realization of a free-standing seismic mass by means of reactive ion etching and sacrificial oxide etching, the mechanical protection of the sensing element with a thin silicon cap bonded onto the structured SOI wafer, and eventually the electrical connection with the ASIC by flip-chip bonding. Preliminary results are very encouraging: dynamic actuation of the sensing elements is optically tested, with a yield of 70% at a prototype level. Excellent shock resistance and low internal stress are observed.

Tuneable microwave devices including fringe effect capacitor incorporating ferroelectric films

Abstract: The present invention relates to a tuneable fringe effect capacitor for conducting radio frequency energy. The capacitor includes a thin film of ferroelectric material, a pair of films of a conductive material deposited on the ferroelectric film with a gap between the films, and a substrate for the ferroelectric material and the conductive films. The capacitance value across the gap is varied by applying a voltage to the ferroelectric material and thereby altering the dielectric constant of the ferroelectric material.

Inductively powered lighting

Abstract: Disclosed is inductive coupling of power to devices having negative resistances, such as gas-filled discharge lamps (fluorescent tubes, neon signs, and the like) from a primary inductive loop, using resonant conditioning of the power provided to the device. A "C" shaped inductor (202) around the loop and a resonating capacitor (406) in parallel with the inductor provide a current source to the lamp (403) from across the capacitor. The circuit is capable of first igniting a lamp using a higher voltage available when the Q of the unloaded circuit is high, then running the lamp or other device at a controlled current. The lamp current is substantially proportional to the primary inductive loop flux, and substantially independent of the lamp resistance. A second inductor (404) in series with the first though not itself a collector of flux acts as a current limit. Applications include lighting, displays (optionally isolated and dimmable), and production of ultraviolet radiation.

A multilevel voltage-source converter system with balanced DC voltages

Abstract: In this paper, a multilevel voltage-source converter system is proposed for high-voltage, high-power applications such as back-to-back interconnection of power systems, large induction motor drives, and electrical traction drives. Multilevel voltage-source converters have a voltage unbalance problem in the DC capacitors. The problem may be solved by use of additional voltage regulators or separate DC sources. However, these solutions are found not to be practicable for most applications. The proposed converter system can solve the voltage unbalance problem of the conventional multilevel voltage-source converters, without using any additional voltage balance circuits or separate voltage sources. The mechanism of the voltage unbalance problem is analyzed theoretically in this paper. The voltage unbalance problem of multilevel converters in the DC capacitors has been solved by the proposed internal connections of the AC/DC and DC/AC converters. The validity of the new converter system is demonstrated by simulation and experiment. >

Electrical properties of ferroelectric thin‐film capacitors with hybrid (Pt,RuO2) electrodes for nonvolatile memory applications

Abstract: For Pb(ZrxTi1−x)O3 (PZT) thin‐film capacitors to be used in ferroelectric nonvolatile memories, they must have low polarization fatigue and low leakage currents. PZT capacitors fabricated in our laboratory with RuO2 electrodes exhibit excellent polarization fatigue characteristics, but they have large and variable leakage currents (typically 10−3–10−4 A/cm2 at 1 V). On the other hand, PZT capacitors with Pt electrodes have low leakage currents (typically <10−9 A/cm2 at 1 V), but they undergo severe polarization fatigue. New (Pt,RuO2) hybrid electrodes which result in PZT capacitors that combine the excellent fatigue behavior of RuO2/PZT/RuO2 with the low leakage currents of Pt/PZT/Pt capacitors have been developed. The hybrid electrodes studied are of two main types: one type consisted of Pt/RuO2 or RuO2/Pt double layers, while the other consisted of a codeposited Pt–RuO2 layer. All capacitors discussed here had an RuO2/PZT/hybrid electrode/MgO heterostructure. It will be shown that capacitors with neglig...

A multilevel voltage-source converter system with balanced DC voltages

Abstract: In this paper, a multilevel voltage-source converter system is proposed for high-voltage, high-power applications such as back-to-back interconnection of power systems, large induction motor drives, and electrical traction drives. Multilevel voltage-source converters have a voltage unbalance problem in the DC capacitors. The problem may be solved by use of additional voltage regulators or separate DC sources. However, these solutions are found not to be practicable for most applications. The proposed converter system can solve the voltage unbalance problem of the conventional multilevel voltage-source converters, without using any additional voltage balance circuits or separate voltage sources. The mechanism of the voltage unbalance problem is analyzed theoretically in this paper. The voltage unbalance problem of multilevel converters in the DC capacitors has been solved by the proposed internal connections of the AC/DC and DC/AC converters. The validity of the new converter system is demonstrated by simulation and experiment. >

Influence of platinum interlayers on the electrical properties of RuO2/Pb(Zr0.53Ti0.47)O3/RuO2 capacitor heterostructures

Abstract: Lead zirconate titanate, Pb(ZrxTi1−x)O3 or PZT, thin films grown on RuO2 electrodes by the sol‐gel process have excellent resistance to polarization fatigue, but they generally have two drawbacks. The films have high leakage currents and large property variation. In this letter we show that the use of a thin Pt layer (100 A) deposited on the bottom RuO2 electrode to fabricate RuO2/PZT/Pt/RuO2/(100)MgO capacitors has two important effects. It reduces capacitor leakage by two to four orders of magnitude and it significantly reduces the large property variation. In addition, these capacitors retain their excellent resistance to polarization fatigue which is characteristic of the RuO2/PZT/RuO2 heterostructure.

Electrical impedance measurements of polymer light-emitting diodes

Abstract: We report electrical impedance measurements of polymer light‐emitting diodes employing the soluble, conjugated polymer poly[2‐methoxy, 5‐(2’‐ethyl‐hexyloxy)‐1,4‐phenylene vinylene] (MEH‐PPV) as the light‐emitting layer. The diode structures were metal‐polymer‐metal structures utilizing thin gold as the transparent, positive contact, and calcium as the negative contact. The devices were fabricated using undoped, polymer active layers ∼40 nm thick. The polymer light‐emitting diodes are accurately modeled as a resistor and capacitor in parallel for frequencies from 100 Hz to 1 MHz and for bias conditions from reverse bias to forward current densities of 0.1 A/cm2. The diode capacitance as a function of bias voltage is qualitatively different from conventional Schottky or p‐n junction diodes; in reverse bias, the polymer layer is fully depleted and the capacitance is independent of bias; at small forward bias, traps are charged near the metallic contacts and the capacitance increases; under large forward bias, with significant electron and hole injection, the traps are neutralized and the capacitance decreases. From the magnitude of the initial increase in capacitance with forward bias the trap density is estimated to be only a few times 1016 cm−3.

Planar microwave and millimeter-wave lumped elements and coupled-line filters using micro-machining techniques

Abstract: Planar microwave and millimeter-wave inductors and capacitors have been fabricated on high-resistivity silicon substrates using micro-machining techniques The inductors and capacitors are suspended on a thin dielectric membrane to reduce the parasitic capacitance to ground The resonant frequencies of a 12 nH and a 17-nH inductor have been increased from 22 GHz and 17 GHz to around 70 GHz and 50 GHz, respectively We also report on the design and measurement of a new class of stripline filters suspended on a thin dielectric membrane Interdigitated filters with 43% and 5% bandwidth have been fabricated and exhibit a port-to-port 07 dB and 20 dB loss, respectively, at 14-15 GHz The micro-machining fabrication technique can be used with silicon and GaAs substrates in microstrip or coplanar-waveguide configurations to result in planar low-loss lumped elements and filters suitable for monolithic integration or surface mount devices up to 100 GHz >

Fast and slow border traps in MOS devices

Abstract: Convergent lines of evidence are reviewed which show that near-interfacial oxide traps (border traps) that exchange charge with the Si can strongly affect the performance, radiation response, and long-term reliability of MOS devices. Observable effects of border traps include capacitance-voltage (C-V) hysteresis, enhanced 1/f noise, compensation of trapped holes, and increased thermally stimulated current in MOS capacitors. Effects of faster (switching times between /spl sim/10/sup -6/ s and /spl sim/1 s) and slower (switching times greater than /spl sim/1 s) border traps have been resolved via a dual-transistor technique. In conjunction with studies of MOS electrical response, electron paramagnetic resonance and spin dependent recombination studies suggest that E' defects (trivalent Si centers in SiO/sub 2/ associated with O vacancies) can function as border traps in MOS devices exposed to ionizing radiation or high-field stress. Hydrogen-related centers may also be border traps.