Showing papers on "Capacitance published in 1981"

On board self-calibration of analog-to-digital and digital-to-analog converters

Abstract: A method and apparatus is disclosed which corrects for errors produced in data acquisition systems. Disclosed is a method and circuit for correcting errors, such as mismatch between binary weighted capacitors and offset, in a charge redistribution, weighted capacitor array analog-to-digital converter. A self-calibrating, self-correcting circuit is comprised of a second binary array of capacitors which adds to the regular charge redistribution capacitor array an error correcting signal to compensate for the mismatch. This error correcting signal is then stored and the other error correcting signals for other capacitors in the regular capacitor array are determined and subsequently stored for later correction of other capacitance mismatch.

Specific capacitance of Josephson tunnel junctions

Abstract: The specific capacitance of several types of Josephson tunnel junctions has been measured by observing resonances in lightly-damped 2-junction interferometers. The capacitance was calculated using the resonance voltage, obtained by analyzing steps in the I-V characteristics, and the interferometer inductance, which was measured directly by the injection of a control current. Using this technique, the specific capacitance C s was determined for tunnel junctions with Pb-In-Au alloy base electrodes and Pb-Bi counterelectrodes, as well as for junctions made on Nb films with Pb-In-Au counterelectrodes. In both cases, barriers were produced by rf plasma oxidation. Junctions with Josephson current densities j 1 between 200 and 5000 A/cm2were investigated. It was found that 1/C s decreased with \log j_{1} , and that at j 1 = 1000 A/cm2, C s was 4.2 ±0.3 μF/cm2for the Pb-alloy junctions and 13.4 ±1 μF/cm2for the Nb junctions. These results are discussed in relation to available data on oxide thickness and dielectric constant.

Noise caused by GaAs mesfets in optical receivers

Abstract: In the application of GaAs metal-semiconductor field effect transistors (MESFETS) in ultra low-noise lightwave receivers, the channel noise is often the dominant effect in determining sensitivity. This paper analyzes for the first time the excess channel-noise factor Γ for GaAs by considering the effect of circuit capacitance, as well as gate-to-source capacitance on the correlation of gate and channel fluctuations, and derives a useful and analytic expression for Γ. For example, we find that Γ for practical GaAs MESFET amplifiers can be much larger than 1.1 as is usually assumed. The multiplication factor, Γ is approximately 1.75 for the practical GaAs MESFET with 1-μm gate length, which explains the discrepancy between the optical sensitivity from the noise calculation and experiments.

Radiation-Induced Trivalent Silicon Defect Buildup at the Si-SiO2 Interface in MOS Structures

Abstract: Electron spin resonance and capacitance versus voltage measurements demonstrate approximately a one-to-one correspondence between the density of radiation-induced trivalent silicon defects at the (111) Si-SiO2 interface and the density of radiation induced electronic interface states.

An Operational Model for Microchannel Plate Devices

Abstract: The behavior of optical detectors using microchannel plates (MCPs) as electron multipliers is described in terms of the physical parameters of the MCP (channel resistance, channel capacitance, channel wall secondary emission ratio, etc.). Three operating modes are included: (1) DC operation at low light levels, (2) pulse detection operation at high peak currents, and (3) single electron counting with cascaded V-plate and Z-plate MCPs.

Electronic Properties of ZnO Varistors: A New Model

Abstract: Much of the research on ZnO varistors has concentrated on the explanation of their dc current-voltage characteristics. However, varistors also have unusual ac properties which can be technologically important, and must be described by any comprehensive model. In an ideal varistor with identical grain boundaries throughout, there should be no dispersive capacitance at zero bias. In real varistors this capacitance varies considerably with frequency. This dispersion has two causes, charge trapping in the depletion regions and differing grain boundary barriers. Calculations for each process are given. For voltages well below the varistor breakdown value, the low frequency capacitance increases with applied voltage. At even higher voltages the capacitance turns over and becomes negative. All of these effects can be described with a double depletion layer/thermionic emission model. The anomalous capacitance behavior with bias is due to the modulation of the potential barriers by charge trapping at the grain boundaries. In the varistor breakdown regime minority carriers created by impact ionization are important.

Fet memory cell structure and process

Abstract: A dense, vertical MOS FET memory cell has a high charge storage capacitance per unit area of substrate surface The charge storage capacitor structure is formed within a well etched in the silicon semiconductor substrate by a combination of reactive ion etching and a self-limiting wet etch

Semiconductor integrated circuit device including means for reducing the amount of potential variation on a reference voltage line

Abstract: In an MOS memory, a reference voltage is generated to determine an input threshold voltage of the input circuit. Noise fed from various signal wirings to the reference voltage wiring via stray capacitances is reduced by a decoupling capacitance formed between the reference voltage wiring and the ground wiring. The decoupling capacitance, however, permits relatively large levels of noise induced on the ground wiring by changes in the operation current of the circuit to be transmitted to the reference voltage wiring. According to this invention, a capacitance which forms a pair with the decoupling capacitance is provided between the power-supply wiring and the reference voltage wiring. Noise induced on the power-supply wiring by a change in the operation current of the circuit is substantially opposite in polarity to the noise induced on the ground wiring. Therefore, the noise fed from the ground wiring to the reference voltage wiring is cancelled by the capacitance provided between the power-supply wiring and the reference voltage wiring.

Bulk and surface states analysis in a‐Si:H by Schottky and MIS tunnel diodes capacitance and conductance measurements

Abstract: An experimental and theoretical study of both the capacitance and the conductance of Schottky and MIS tunnel diodes made on undoped a‐SI:H, versus frequency, temperature, and voltage is presented in this paper. It is based on a general model using an equivalent electrical circuit of the devices, which permits an unambiguous distinction to be made between the contributions of bulk surface states, to determine their respective densities and to analyze their kinetic properties, It is shown that the bulk density of states (DOS) can be determined from capacitance and conductance measurements versus temperature and frequency on both Schottky and MIS devices, provided the modulation frequency is high enough to prevent any contribution from surface states. It is demonstrated that capacitance‐voltage characteristics of Schottky diodes cannot provide reliable information about either bulk or surface as the diffusion theory and not the thermionic theory is appropriate to describe the transport of electrons across th...

Capacitive touch panel control

Abstract: A capacitive touch panel control provided with first and second conductive circuit pads on opposite faces of a thin dielectric sheet in the form of a film secured to a dielectric panel by adhesive. The panel is provided with a touch pad. The circuit pads are disposed so that at least a portion of each is in appositional facial registration with the touch pad and out of appositional facial registration with each other so as to provide a variable capacitance between the circuit pads as an incident of selective touching and non-touching of the touch pad by a user. The circuit pads may form a portion of a printed circuit on the film which further includes electrical conductors for making connection to associated apparatus. Ground conductors may be provided on the film adjacent the output voltage conductors of the circuit to reduce leakage between the circuit conductors. The provision of the circuit pads on opposite faces of the film permits electrically insulated crossover of the conductors for facilitated layout of the circuit.

Analysis and synthesis of switched-capacitor state-variable filters

Abstract: The design and analysis of switched-capacitor filters of the state variable or "leapfrog" type is presented in which the sampling rate may be as low as twice the highest frequency of interest. The effects due to the sampled data nature of the signals are fully taken into account and an exact synthesis is derived. This allows the sampling rate to be treated as a design parameter which Influences the maximum attenuation level in the stopband and the required capacitance ratios.

Depletion layer effects in the open-circuit- voltage-decay lifetime measurement

Abstract: There is a renewal of interest in open circuit voltage decay as a technique for determining the base region minority carrier lifetime in semiconductor diodes. Although the existing theory of open circuit voltage decay provides a substantial foundation for interpreting the experimental data, major features of the decay curves of real silicon diodes cannot be satisfactorily explained unless depletion layer effects are taken into account. Theoretical decay curves are calculated to show the effects of depletion layer capacitance and recombination current on the otherwise ideal open circuit voltage decay. From these and from experimental decay curves, it is shown that each of these depletion layer effects is significant only below a threshold junction voltage that depends upon material parameters of the device.

Semiconductor Electrodes XXXVI . Characteristics of , Electrodes in Aqueous Solution

Abstract: Capacitance and voltammetric measurements were employed to investigate the electrochemical and photoelectrochemical (PEC) behavior of ,, and single crystal electrodes in aqueous solutions containing various redox couples (, , , Fe2+/ Fe3+, , and , where HV is heptyl viologen and MV is methyl viologen) In supporting electrolyte , the conduction bandedges of and , determined from the capacitance measurement, are at −014 and −044V vs SCE, respectively, and the valence bandedge of is at 093V vs SCE A bandgap of 14 eV for was determined either from the photocurrent action spectrum or from the capacitance measurement The specific effects of iodide on the capacitance and voltammetric behavior of layer‐type compounds are compared The characteristics of several PEC cells are also described

Fast recharge output circuit

Abstract: A body implantable stimulator having an output capacitance that is periodically charged to a predetermined energy level and discharged through an electrode coupled to body tissue. The discharge pulse width is controlled by a semiconductor switch and after a short delay the capacitor is recharged rapidly to its original charge. The recharge current is regulated by a differential circuit responsive to the voltage on a reference capacitor and the output capacitor, both capacitors being coupled to the active electrode.

Planar doped barrier semiconductor device

Abstract: Disclosed is a majority carrier rectifying barrier semiconductor device housing a planar doped barrier. The device is fabricated in GaAs by an epitaxial growth process which results in an n+ -i-p+ -i-n+ semiconductor structure wherein an extremely narrow p+ planar doped region is positioned in adjoining regions of nominally undoped (intrinsic) semiconductive material. The narrow widths of the undoped regions and the high densities of the ionized impurities within the space charge region results in rectangular and triangular electric fields and potential barriers, respectively. Independent and continuous control of the barrier height and the asymmetry of the current vs. voltage characteristic is provided through variation of the acceptor charge density and the undoped region widths. Additionally, the capacitance of the device is substantially constant with respect to bias voltage.

Charge control of the heterojunction two-dimensional electron gas for MESFET application

Abstract: Previous works have shown that a two-dimensional electron gas (2 DEG) is accumulated at the interface of GaAs (n)/Al x Ga 1-x As (n) isotype heterojunctions. In this paper, a MESFET structure working with this 2 DEG is presented. Theoretical treatments are given, considering that the charge control results from the interpenetration of the Schottky space-charge region and the accumulation layer. A semi-analytical calculation is then developed: conductance, capacitance, source-to-drain current at saturation, and transconductance are predicted for a large-gate FET. Source-to-drain saturation current in short-gate FET is also given. Experimental results obtained in our laboratory and those recently published are compared to calculated data. The good agreement observed in all cases, including low-temperature measurements, clearly shows that the 2 DEG MESFET behavior is actually valid. The high mobility of electrons One can expect from the 2 DEG, particularly at 77 K, suggests that the 2 DEG MESFET is a promising device for microwave and high-speed devices.

Rod-like probe for the capacitive measurement of the level in a container

Abstract: Disclosed is a capacitance level measuring device comprised of a container whose level is to be measured and a probe inserted into and spaced from the container. The capacitance between the probe and container varies in relation to the level in the container. A capacitance measuring circuit determines the capacitance between the probe and container and thus indicates the level in the container. The integrity of the probe is verified by constructing the probe so as to include it in a series circuit, as well as the capacitance measuring circuit, and a lack of continuity in the probe is indicative of questionable probe integrity. The question as to the probe's integrity would indicate a questionable level indication from the capacitance measuring circuit. Various probe constructions are also disclosed.

Dielectric components of charge movements in skeletal muscle.

Abstract: 1. Voltage clamp experiments measured transients from 10 mV steps applied about different membrane potentials, VT. Their analysis employed the Fourier transform relationship between dielectric spectra of permittivity as a function of frequency, and the step transient admittance, as well as established methods. 2. The membrane capacitance measured between -85 mV and about -50 mV rose monotonically and was associated with simple decaying transients in both ‘on’ and ‘off’ steps. At more depolarized potentials the capacitance increased sharply and was associated with a charging current of complex form, before falling again beyond the transition potential. 3. Step-transient responses for dielectric analysis were sampled in the above voltage range. Dielectric spectra of the non-linear transients were obtained by subtracting Fourier transforms of transients at VC = -85 mV from test transforms at VT. 4. The imaginary transform coefficients represent a spectrum of dielectric loss against frequency. These showed two non-linear components. The q beta component formed a broad peak, when charge movements were simple monotonic decays. A sharp low-frequency q gamma peak became superimposed at particular voltages when charge-movement kinetics became complex. 5. In contrast, ‘off’ transients were simple monotonic relaxations. Their transforms showed only one dielectric loss peak, whose frequency was relatively voltage-independent when q gamma occurred in ‘on’ transforms. 6. Both altering holding potential from VH = -85 to -50 mV and adding 1 mM-tetracaine to the bathing solution reduced the dependence of capacitance on voltage. The non-linear polarization currents became simple monotonic relaxations at both the beginning and end of the voltage step. 7. It is concluded that charge movements are composed of at least two components: q beta, and the tetracaine and voltage-inactivated q gamma. Any causal relationship between q beta and q gamma and the membrane processes they might underlie would be expected to be complex.

Multiplexed varistor-controlled liquid crystal display

Abstract: An improved varistor-controlled multiplexed liquid crystal display of the type having columns of front electrodes and rows of rear electrodes connected in series with combinations of varistor elements and electrical capacitances, has a capacitance of increased magnitude formed in parallel with the capacitance of the liquid crystal layer in each of the multiplicity of the display cells, for reducing capacitive crosstalk between an addressed and unaddressed cell elements of the display. The increased capacitance is provided by auxiliary data electrodes positioned below, and spaced by a thin film dielectric layer from, the reflective rear cell row electrodes of the display, and spaced from the varistor member by at least one thick film dielectric layer. A pair of thick film layers may support the row scan electrodes therebetween, or the scan electrodes may be formed between a single layer and the varistor surface.

Magnetotransconductance mobility measurements of GaAs MESFET's

Abstract: It is demonstrated that the magnetic field dependence of the transconductance of short-gate GaAs FET's provides a direct means of characterizing the mobility profile of the active layer of the device, which does not require a capacitance measurement, and which is relatively insensitive to the parasitic series resistance associated with the source and drain contacts. The results are shown to be in agreement with those obtained from conventional measurements on a long-gate FET test structure.

Isothermal Capacitance Transient Spectroscopy

Abstract: A new measurement method for deep levels in semiconductors is demonstrated, by which the measurement of the transient change of capacitance is performed under an isothermal condition (Isothermal Capacitance Transient Spectroscopy). The method allows us to construct a precise measurement and analysis system by a programmable calculator. Detailed experiment and analysis by the method in the case of Au-doped Si in dicate that the method is one of useful tools for spectroscopic analysis of deep levels in semiconductors.

Power factor correction system

Abstract: A discrete-time, closed loop power factor corrector system controls the coupling of a delta-connected switched capacitor array to a 3- or 4-wire power line which may have time-varying, unbalanced, inductive loads. For inductive loads that cannot be exactly compensated with a delta-connected capacitance, the corrector system minimizes the total RMS reactive current drawn from the power line.

Capacitance intrusion detection system

Abstract: A capacitance intrusion detection system for use with a metal object or objects insulated from ground comprises a circuit for cyclically charging and discharging the object at a relatively low frequency, for example, less than 500 Hz, and simultaneously integrating the charge on the object to develop a DC voltage proportional to the capacitance of the object. The integrating network is AC coupled to a bandpass filter which passes signals having frequencies corresponding to changes in capacitance of the object caused by an intruder and these signals are applied to a threshold circuit for activating an alarm when an intrusion occurs. Tamper alarm circuits are provided to detect unauthorized disconnection of any portion of the protected object (decrease capacitance) or the addition of capacitance in an attempt to defeat the system.