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Showing papers on "Capacitance published in 1988"


Journal ArticleDOI
TL;DR: In this paper, a two-dimensional electron gas (2DEG) in a quantum well or inversion layer, unlike an ordinary grounded metallic plane, does not completely screen an applied transverse electric field, but partial penetration of an external field through a highly conducting 2DEG allows the implementation of several novel high-speed devices, including a threeterminal resonant tunneling transistor and a gate-controlled thermionic emission transistor.
Abstract: Two‐dimensional electron gas (2DEG) in a quantum well or inversion layer, unlike an ordinary grounded metallic plane, does not completely screen an applied transverse electric field. Owing to its Fermi degeneracy energy, a 2DEG manifests itself as a capacitor in series, whose capacitance per unit area equals CQ=me2/πℏ2, where m is the effective electron mass in the direction transverse to the quantum well. Partial penetration of an external field through a highly conducting 2DEG allows the implementation of several novel high‐speed devices, including a three‐terminal resonant‐tunneling transistor and a gate‐controlled thermionic emission transistor.

793 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate the usefulness and high sensitivity of the atomic force microscope (AFM) for imaging surface dielectric properties and for potentiometry through the detection of electrostatic forces.
Abstract: We demonstrate the usefulness and high sensitivity of the atomic force microscope (AFM) for imaging surface dielectric properties and for potentiometry through the detection of electrostatic forces Electric forces as small as 10−10 N have been measured, corresponding to a capacitance of 10−19 farad The sensitivity of our AFM should ultimately allow us to detect capacitances as low as 8×10−22 F The method enables us to detect the presence of dielectric material over Si, and to measure the voltage in a p‐n junction with submicron spatial resolution

688 citations


Journal ArticleDOI
TL;DR: Two methods are described for estimation of passive cell parameters such as membrane capacitance, membrane conductance and access resistance in tight-seal whole cell recording by using a time domain technique and a lock-in amplifier.
Abstract: Two methods are described for estimation of passive cell parameters such as membrane capacitance, membrane conductance and access resistance in tight-seal whole cell recording. Both methods are restricted in their application to cases where the cell under study can be approximated by a simple three-component network with linear properties over some voltage range. One method, referred to as the time domain technique, requires only standard electrophysiological equipment and a computer. Parameters are derived from an analysis of capacitive transients during square wave stimulation. It is readily adaptable to wide variations in experimental parameters. Particurlarly, it is equally applicable to the “slow whole-cell” configuration (access resistance in the range 100 MΩ to 1 GΩ) and to normal whole-cell measurements (access resistance typically 10 MΩ). The other method applies a sine wave command signal to the cell and employs a lock-in amplifier to analyse the resulting current signal. Two modes of operating the lock-in amplifier are described. One mode provides an output signal directly proportional to small changes in capacitance at maximum resolution (1–10 fF). The other mode, in conjunction with a digital computer, supplies estimates of all passive cell parameters, as does the time domain technique, but with a large amount of data reduction performed by the lock-in amplifier itself. Due to the special hardware, however, this method is not as flexible as the time domain technique.

609 citations


Journal ArticleDOI
11 Apr 1988
TL;DR: In this paper, a novel multiresonant switch concept is proposed to overcome the parasitic oscillations caused by the junction capacitance of the rectifying diode, which results in favorable switching conditions for all devices.
Abstract: The power transistor in zero-current-switched quasiresonant converters (ZCS-QRCs) suffers from excessive voltage stress, and the converter regulation characteristics and stability are adversely affected by parasitic oscillations caused by the junction capacitance of the rectifying diode. A novel, multiresonant switch concept is proposed to overcome these problems. A unique multiresonant network arrangement results in absorption of all parasitic components, including transistor output capacitance, diode junction capacitance, and transformer leakage inductance, in the resonant circuit. This results in favorable switching conditions for all devices. Experimental results show that ZVS multiresonant converters are superior to ZVS-QRCs due to reduced transistor voltage stress and improved load range and stability. >

344 citations


Patent
03 May 1988
TL;DR: In this paper, an apparatus for detecting the presence and/or measuring the concentration of an analyte (24) in the fluid medium is described. But it relies on biospecific binding between a biochemical binding system and the analyte to change the dielectric properties of a capacitive affinity sensor.
Abstract: An apparatus for detecting the presence and/or measuring the concentration of an analyte (24) in the fluid medium (22) is disclosed. The apparatus relies on biospecific binding between a biochemical binding system (20) and the analyte (24) to change the dielectric properties of a capacitive affinity sensor. The biological affinity sensor is optimized by: adjusting the thickness and dielectric properties of a passivation layer (16) to generally match the impedance of the biological binding system (20, 21); and minimize the double layer capacitance so that bulk capacitance changes associated with the biological binding system (20, 21) are maximized.

252 citations


Journal ArticleDOI
TL;DR: Measured capacitance in excess of the space-charge capacitance is shown to be caused by the injection of minority carriers into the bulk semiconductor, rather than by the presence of interface states, as previously thought.
Abstract: We identify the physical origin of the excess capacitance at Schottky diodes without an interfacial layer, i.e., intimate Schottky contacts. Measured capacitance in excess of the space-charge capacitance is shown to be caused by the injection of minority carriers into the bulk semiconductor, rather than by the presence of interface states, as previously thought. Minority-carrier injection depends sensitively on the properties of the Ohmic back-contact.

199 citations


Journal ArticleDOI
TL;DR: In this article, the effects of stray capacitances on the measurement system must be minimized, in order to achieve high measurement sensitivity and good signal-to-noise ratio.
Abstract: Reviews existing instrumental techniques suitable for industrial measurement of capacitance in the range 0.1-10 pF, including resonance, oscillation, charge/discharge and AC bridge methods. It shows that in order to achieve high measurement sensitivity and good signal-to-noise ratio, the effects of stray capacitances on the measurement systems must be minimised. Several intrinsically stray-immune measuring circuits are described, including an audio-frequency transformer-ratio-arm bridge and a charge/discharge measuring circuit capable of operating at frequencies up to several MHz. The active guard method and suitable guard driving techniques for reducing the effects of strays on the measurement of grounded capacitances sensors are described. Techniques for reducing the baseline drift of the capacitance measuring circuits, such as auto-balancing and auto-calibration, etc., are also discussed.

191 citations



Patent
13 Jul 1988
TL;DR: In this article, an apparatus for monitoring the state of charge of a battery having a shunt resistor connected in series with a battery and an integrating circuit connected across the terminals of the Shunt resistor is provided.
Abstract: An apparatus for monitoring the state of charge of a battery having a shunt resistor connected in series with a battery and an integrating circuit connected across the terminals of the shunt resistor is provided. The integrating circuit includes a Memoriode having a large capacitance and the capability to store charge for long periods of time, so that the integration can be performed along the same curve even if power to the integrating circuit is interrupted.

162 citations


Journal ArticleDOI
TL;DR: Using the sequential theory of resonant tunneling, the dc currentvoltage characteristic of a double-barrier structure is calculated, taking into account the effect of space charge in the quantum well as mentioned in this paper.
Abstract: Using the sequential theory of resonant tunneling, the dc current‐voltage characteristic of a double‐barrier structure is calculated, taking into account the effect of space charge in the quantum well. A region of current bistability is found over a voltage range which is determined by the maximum space charge and the capacitance of the structure. These parameters are directly related to the periodicity of magnetoquantum oscillations in the current.

161 citations


Journal ArticleDOI
TL;DR: In this article, a liquid hold-up gauge based on the measurement of the electrical impedance has been developed for application in gas-liquid pipe flow, which consists of two ring electrodes mounted flush to the pipe wall.

Journal ArticleDOI
TL;DR: It is shown that the measured capacitance of a secretory granule can be up to 80% smaller than its true value, during the course of a typical mast cell degranulation, and described a software-based phase-detector that simplifies capacitance measurements.

Journal ArticleDOI
TL;DR: In this article, an instrumentation system for obtaining cross-sectional images of two-component flows is described, which uses measurements made with capacitance electrodes mounted on the outer surface of the fluid-conveying pipe, and an image reconstruction algorithm based on backprojection.
Abstract: An instrumentation system for obtaining cross-sectional images of two-component flows is described. It uses measurements made with capacitance electrodes mounted on the outer surface of the fluid-conveying pipe, and an image reconstruction algorithm based on backprojection. Images of static physical models simulating a stratified solids/air flow are presented.

Journal ArticleDOI
02 Oct 1988
TL;DR: A single-phase induction motor using a novel electronically controlled capacitor using a DC capacitor switched by a transistor H bridge and a continuously variable capacitance in series with the auxiliary winding is described.
Abstract: A single-phase induction motor using an electronically controlled capacitor is described. The system uses a DC capacitor switched by a transistor H bridge. By proper control of the transistor switching, the circuit synthesizes a continuously variable capacitance in series with the auxiliary winding. The system could be used to replace standard single-phase motor capacitor configurations to provide improved machine performance. The basic system is described and compared with a normal capacitor-run motor. The effects of independent adjustments in several system parameters are considered, and the circuit device requirements are described. Both analog and digital simulations are used to carry out the analysis. Illustrations of some of the design flexibility inherent in the system are included. >

Journal ArticleDOI
E. Barke1
TL;DR: It is shown that with up-to-date dimensions, the simple parallel-plate model is no longer adequate, and easy- to-use and fast-To-compute formulas exist that result in accurate and reliable capacitance values.
Abstract: A comparison is made between various approximations of the line-to-ground capacitance problem in a VLSI environment. It is shown that with up-to-date dimensions, the simple parallel-plate model is no longer adequate. However, easy-to-use and fast-to-compute formulas exist that result in accurate and reliable capacitance values. >

Journal ArticleDOI
TL;DR: In this article, an analytic large-signal model for the GaAs MESFET is presented, which describes the conduction and displacement currents of the FET as a function of instantaneous terminal voltages and their time derivatives.
Abstract: An analytic, large-signal model for the GaAs MESFET is presented. The device model is physics-based and describes the conduction and displacement currents of the FET as a function of instantaneous terminal voltages and their time derivatives. The model allows arbitrary doping profiles in the channel and is thus suitable for the optimization of ion-implanted and buried-channel FETs. It also accounts for charge accumulation in the conducting channel at high electric fields and the associated capacitance in a self-consistent manner. Theoretical predictions of the model are correlated with experimental data on X-band power FETs and excellent agreement is obtained. >

PatentDOI
TL;DR: In this paper, an electroacoustic transducer is described, which consists of a substrate of a semiconductor material with a recessed portion, where a membrane is stretched across the recessed part, which membrane is set in vibration in response to an input signal comprising audio and/or ultrasonorous frequencies.
Abstract: This invention provides an electroacoustic transducer and a method of making it. The transducer according to the invention comprises a substrate of a semiconductor material with a recessed portion. A membrane is stretched across the recessed portion, which membrane is set in vibration in response to an input signal comprising audio and/or ultrasonorous frequencies. A pair of electrodes is provided, which form a capacitor, and between which an electric field is present. The electrodes are so arranged relatively to the membrane that the capacitance of the capacitor can vary under the influence of vibrations of the membrane, so that acoustic signals are converted into electric signals. A layer of an electrically insulating material functions as a carrier for an electric charge to provide an auxiliary electric field between the electrodes. The transducer is characterized in that the peripheral edge of the substrate, which is raised relatively to the recessed portion, has a set of openings formed in it, each extending through the substrate. The membrane is attached through the openings to the peripheral edge.

Journal ArticleDOI
TL;DR: In this paper, the formation and properties of monolayers of di-oleoyl lecithin (di-O-PC) at the mercury/water interface are reported.

Journal ArticleDOI
TL;DR: In this article, a stray-immune capacitance measuring instrument based on the charge transfer principle is described, which has a programmable measurement frequency up to several megahertz and is inexpensive and suitable for integration onto a single chip.
Abstract: A stray-immune capacitance measuring instrument based on the charge transfer principle is described. It has a programmable measurement frequency up to several megahertz and is inexpensive and suitable for integration onto a single chip. The effects of stray capacitances, including those of the switching components, have been eliminated by using a special switching arrangement, resulting in a baseline drift of 0.02 pF (at 1-MHz measurement frequency) over a 12-h period. >

Journal ArticleDOI
TL;DR: In this article, a monolithic diode grid was fabricated on 2-cm/sup 2/ gallium-arsenide wafers in a proof-of-principle test of a quasi-optical varactor millimeter-wave frequency multiplier array concept.
Abstract: Monolithic diode grid were fabricated on 2-cm/sup 2/ gallium-arsenide wafers in a proof-of-principle test of a quasi-optical varactor millimeter-wave frequency multiplier array concept. An equivalent circuit model based on a transmission-line analysis of plane wave illumination was applied to predict the array performance. The doubler experiments were performed under far-field illumination conditions. A second-harmonic conversion efficiency of 9.5% and output powers of 0.5 W were achieved at 66 GHz when the diode grid was pumped with a pulsed source at 33 GHz. This grid had 760 Schottky-barrier varactor diodes. The average series resistance was 27 Omega , the minimum capacitance was 18 fF at a reverse breakdown voltage of -3 V. The measurements indicate that the diode grid is a feasible device for generating watt-level powers at millimeter frequencies and that substantial improvement is possible by improving the diode breakdown voltage. >

Journal ArticleDOI
TL;DR: In this article, the relationship among the speed of response, the signal-to-noise ratio and the charge collection time in ionization chamber calorimeters is analyzed, and it is shown that a dominant limiting factor to the response is the charge transfer time from the electrodes to the amplifier determined by the electrode capacitance CD and the inductance of connections.
Abstract: Relations among the speed of response, the signal-to-noise ratio and the charge collection time in ionization chamber calorimeters are analyzed. A dominant limiting factor to the speed of response is the charge transfer time from the electrodes to the amplifier determined by the electrode capacitance CD and the inductance of connections Ls. The time parameter L s C D sol1 2 has to be at least an order of magnitude smaller than the required length of the overall calorimeter response. The charge collection time plays a secondary role in determining the speed of response, while together with the charge yield it affects the signal-to-noise ratio.

Journal ArticleDOI
TL;DR: Ketchen et al. as discussed by the authors showed that to first order, the sliding-contact generation site has no capacitance, and this conclusion was further supported by a double sliding contact experiment where, to first-order, neither the generation nor the detection site has any capacitance.
Abstract: By reanalyzing an earlier experiment to generate subpicosecond pulses using photoconductive switches (M.B. Ketchen, et al., Appl. Phys. Lett., vol.48, pp.751-753, 1986), it is shown that to first order, the sliding-contact generation site has no capacitance. This conclusion is further supported by a double sliding-contact experiment where, to first order, neither the generation nor the detection site has any capacitance. This result removes the parasitic capacitance of the electrical circuit as one of the major difficulties to short electrical pulse generation using photoconductive switches. >

Journal ArticleDOI
TL;DR: In this article, a nonissipative LC turn-off snubber is used to reduce the voltage stress on a switching transistor, which is caused by the energy stored in the transformer leakage inductance.
Abstract: A nondissipative LC turn-off snubber is used to reduce the voltage stress on a switching transistor, which is caused by the energy stored in the transformer leakage inductance. A detailed analysis of the fundamental characteristics of a buck-boost converter with an LC snubber is given, clarifying the effect of the snubber capacitance. In particular, it is found that the transformer current increases with the snubber capacitance, the transistor surge voltage and power loss are evaluated, and the optimum value of the snubber capacitance is derived. The most effective value of the snubber inductance is also discussed. >

Patent
Walter Lee Davis1
19 Dec 1988
TL;DR: In this paper, a low power and low voltage frequency synthesizer includes a memory containing information to provide divisor information to the variable divider of a phase locked loop and information to select predetermined values of capacitance to connect to the frequency determining resonant network of the VCO.
Abstract: A low power and low voltage frequency synthesizer includes a memory (22) containing information to provide divisor information to the variable divider (20) of a phase locked loop and information to select predetermined values of capacitance to connect to the frequency determining resonant network of the VCO (18) to provide a coarse tuning. This tuning is then further modified by the normal operation of the phase locked loop.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the kinetics of the adsorption of albumin on a platinum rotating disk electrode using impedance measurements and proposed a model of two consecutive reactions occuring at the interface.

Patent
13 May 1988
TL;DR: In this paper, a single fluid-pressure transducer unit, of the type in which sensed electrical capacitance is varied in accordance with electrode deflections induced by pressure changes, is rendered capable of characterizing a wide range of pressures extending from near-vacuum to atmospheric levels, with the aid of a distinctive composite-electrode capsule which interacts uniquely with a conventional type of sheetmetal diaphragm.
Abstract: A single fluid-pressure transducer unit, of the type in which sensed electrical capacitance is varied in accordance with electrode deflections induced by pressure changes, is rendered capable of characterizing a wide range of pressures extending from near-vacuum to atmospheric levels, with the aid of a distinctive composite-electrode capsule which interacts uniquely with a conventional type of sheet-metal diaphragm. While sensing relatively low pressures, the exhibited capacitance of the transducer is essentially that appearing between the diaphragm and a nearby electrode carried by the capsule, but, at or near atmospheric pressure, the diaphragm physically engages and deflects that electrode, which is elastically deformable, causing it to vary a further capacitance appearing between that deformable electrode and a companion stationary electrode which is also part of the capsule.

Journal ArticleDOI
TL;DR: In this article, the difference between two capacitors is measured digitally using a charge redistribution technique incorporating a comparator, MOS switches, a successive approximation register, and a digital-to-analog converter.
Abstract: The difference between two capacitors is measured digitally using a charge redistribution technique incorporating a comparator, MOS switches, a successive approximation register, and a digital-to-analog converter. The technique is insensitive to comparator offset and parasitic capacitance, and the effect of MOS switch charge injection is measured and canceled. Extensive measurements have been made from test chips fabricated in 3- mu m CMOS technology. Detection of percent differences of >

Journal ArticleDOI
TL;DR: The use of polymer dielectrics, particularly biaxially oriented polypropylene (BOPP), has revolutionized power distribution around the world as mentioned in this paper and has been used for power distribution.
Abstract: The use of polymer dielectrics, particularly biaxially oriented polypropylene (BOPP), has revolutionized power distribution around the world. BOPP film of sub mil thickness has displaced impregnated Kraft paper because of superior dielectric performance, lower cost, and small volume. The polypropylene molecule has a unique set of properties which combine stable dielectric properties in the operating temperature and frequency range along with an adequate dielectric constant. High levels of orientation and a small unbalance of orientation are required to produce films of high dielectric strength over large areas of film. Control of thickness uniformities to approximately ± 5 percent are critical to the reliable operation of the capacitor under load and to control of capacitance in the product. A special fibrillated surface is required which promotes complete impregnation by the dielectric fluid. This surface is acquired by the development of a specific crystal morphology at one surface of the film. No additives are used to promote this crystalline structure since most additives effect dissipation factor and generate unwanted heat. Similarly, control of contamination (ppm and ppb) is a key factor in the manufacture of film power capacitors.

Journal ArticleDOI
TL;DR: In this paper, a pseudomorphic Si interlayer, about 1.0 nm thick, is introduced to improve the MIS characteristics of the SiO2/GaAs system, and the Si layer minimises the formation of any detrimental native oxides and thus controls the chemical nature of the GaAs surface.
Abstract: The introduction of a pseudomorphic Si interlayer, about 1.0 nm thick, is found to dramatically improve the MIS characteristics of the SiO2/GaAs system. Quasistatic and high-frequency capacitance/voltage (C/V) data from such a novel capacitor structure on n-GaAs indicate that the surface of the GaAs is swept from inversion to accumulation. X-ray photoelectron spectroscopy and ion scattering spectroscopy confirm the presence of the Si layer and its complete coverage of the GaAs surface. The Si layer minimises the formation of any detrimental native oxides and thus controls the chemical nature of the GaAs surface. This approach has implications in the development of metal-insulator-semiconductor systems in general.

Patent
15 Aug 1988
TL;DR: In this paper, the ink in an ink jet is sensed by a capacitor, one plate of which is coupled to ground through the ink, and the absence of ink will appear as a decreased amount of capacitance.
Abstract: The ink in an ink jet is sensed by a capacitor, one plate of which is coupled to ground through the ink. The absence of ink will appear as a decreased amount of capacitance. In this case the charge of the capacitor will leak off faster, and a sample and hold circuit can sense this to output a signal indicating the absence of ink. The charging signal can either be generated on the chip, which is made from silicon, or can be supplied to the chip. The number of pins on the chip taken for this sensing function can be minimized by multplexing the states of signals supplied to the chip for other purposes to generate the necessary signals to control and operate this sensor.