Showing papers on "Rise time published in 2001"

Characterization of CdTe and CdZnTe detectors for gamma-ray imaging applications

Abstract: CEA-LETI in association with Bicron and Crismatec has been developing solid-state gamma camera technology based on CZT. The project included gamma camera head systems development including front-end electronics with an integrated circuit (ASIC), material growth, and detector fabrication and characterization. One feature of the work is the use of linear correlation between the amplitude and the fast rise time of the signal – which corresponds to the electron transit time in the detector, a development that was reported previously and which allows more than 80% of the 122 keV γ-photons incident on HPBM material to be recovered in a ±6.5% 2D window. In the current work, we summarize other methods to improve CZT detector performance and compare them with the Bi-Parametric Spectrum (BPS) method. The BPS method can also be applied as a diagnositic. BPS curve shapes are shown to vary with electric field, and with electron transport properties, and the correction algorithims are seen to be robust over a range of values. In addition, the technique is found to improve detectors from a variety of sources including some with special electrode geometries. In all cases, the BPS method improves efficiency (>75%) without degrading energy resolution (± 6.5% 2D window) even for a monolithic detector. The method does not overcome bulk inhomogeneity nor noise which comes from low resistivity.

Exploiting the on-chip inductance in high-speed clock distribution networks

Abstract: On-chip inductance effects can be used to improve the performance of high-speed integrated circuits. Specifically, inductance improves the signal slew rate (the rise time), virtually eliminates short-circuit power consumption and reduces the area of the active devices and repeaters inserted to optimize the performance of long interconnects. These positive effects suggest the development of design strategies that benefit from on-chip inductance. An example of a clock distribution network is presented to illustrate the process in which inductance can be used to improve the performance of high-speed integrated circuits.

UWB and EMP susceptibility of modern electronics

Abstract: The susceptibility of different types of single microcontrollers and complex microprocessor-boards to unipolar fast rise time pulses is determined. Rise times down to 100 ps and field amplitudes up to 50 kV/m have been applied to the devices.

A 10 kW high-voltage pulse generator for corona plasma generation

Abstract: In this article we discuss a 10 kW high-voltage pulse generator for producing corona-induced plasma. The generator mainly consists of a three-step resonant charging circuit switched by thyristors, a transmission line transformer, and a triggered spark-gap switch. Voltage pulses of 30–100 kV with a rise time of about 20 ns, a pulse duration of 50–250 ns, pulse repetition rate of 1–900 pulses per second, energy of up to 12 J/pulse, and an average power of up to 10 kW have been achieved with a total energy transfer efficiency of about 80%–90%. At each frequency, the deviation of the energy per pulse is around 1.0%. Moreover, the generator has been tested for more than 100 h for both industrial demonstrations and laboratory investigations at an average output power of 1–10 kW.

Micromagnetic study of switching speed in perpendicular recording media

Abstract: Switching speed in perpendicular recording media has been studied from micromagnetic simulations, by applying a uniform reversal field to an array of magnetic grains. Increasing the damping constant reduces the switching time, but a weak exchange interaction leads to an increase in the switching time. A linear relationship is found between the switching time and the head field rise time for different field strengths, damping constants and weak exchanges. A 20/spl deg/ field angle to the perpendicular direction substantially improves the switching speed.

100 ns current rise time LTD stage

Abstract: Summary form only given. LTD stages are designed to be used as primary storage of pulsed power generators. Their main difference compared to the Marx scheme is ground potential on the stage housing during the shot. This reduces the dimensions of the storage, makes it flexible for reconstruction, simplifies the assembling and maintenance. Other advantage of the grounded housing is the possibility to trigger each stage from the external trigger circuit. This allows to distribute the current flow inside the stage in multiple parallel channels, reducing the equivalent inductance and the current rise time. Previously LTD stages providing 1000 ns and 400 ns current rise time were reported (Bastrikov et al., 1997, Kim et al., 1999). This report presents the design and test results of a fast LTD stage with 100 ns current rise time.

Influence of Rise Time of Pulse Voltage on the Pulsed Plasma Conversion of Methane

Abstract: Recently, the authors developed a high-frequency pulsed plasma for methane conversion to acetylene and hydrogen. Such a pulsed plasma is potentially competitive to the commercial acetylene production processes. For the industrialization of this plasma technology, the influence of some factors, such as the pulse voltage, rise time of pulse voltage, pulse frequency, kind of background gases, temperature of the background gases, and electrode geometries, on methane conversion and the development of a pulse power supply should be cleared. In this study, the influence of the rise time of the pulse voltage on methane conversion has been investigated using a coaxial cylindrical type of reactor. The pulsed streamer/spark discharge occurred more easily with a pulse voltage of short rise time than with that of long rise time. The energy injection rate into the discharge space decreased with increasing the rise time of the pulse voltage. The rise time of the pulse voltage did not remarkably influence the methane con...

Regulator design for inductive booster pump using pulse width modulation technique

Abstract: A DC voltage boost circuit including a regulation circuit that produces a pulse width modulated control signal for regulating the output of the DC voltage boost circuit. Various embodiments of regulation circuits are disclosed. In one embodiment, the regulation circuit includes a waveform generator for generating a triangular waveform and a comparator for producing the pulse width modulated control signal by comparing the triangular waveform with a voltage that varies proportional to the booster output voltage. In another embodiment, the regulation circuit includes a waveform generator for generating a sawtooth waveform whose rise time varies inversely with the booster output voltage and a comparator for producing the pulse width modulated control signal by comparing the modulated sawtooth waveform with a substantially constant voltage. Yet, in another embodiment, the regulation circuit includes a counter for generating a count that sequentially cycles in response to a clock signal, wherein the counter is reset in response to change in the booster output voltage, and a logic circuit for generating the pulse width modulated control signal from the count.

Active pullup circuitry for open-drain signals

Abstract: Circuitry and methods are provided for reducing rise time associated with signals on an open-drain or open-collector signal line Signal line voltage is monitored to determine if the signal line is being pulled LOW If the signal line is not being pulled LOW, as indicated by signal line voltage exceeding a threshold level, additional pullup current is provided The additional current may be provided gradually in relation to the signal line voltage, or may be provided in full whenever voltage exceeds the threshold Circuitry may also be provided to monitor voltage slew rate on the signal line, and to enable the additional pullup current only when the slew rate exceeds a positive threshold level

Electrical excitation circuit for a pulsed gas laser

Abstract: Method and system for providing an excimer or molecular fluorine laser including a laser tube filled with a laser gas surrounded by an optical resonator, where the laser tube has multiple electrodes including a pair of main discharge electrodes connected to a discharge circuit for exciting the laser gas to produce a laser output beam. The discharge circuit has an all solid state switch and preferably does not include a transformer. The solid state switch includes multiple solid state devices that may be capable of switching voltages in excess of 12 kV, such as 14-32 kV or more, or the voltage needed to switch the laser. The series of switches has a rise time of approximately less than 300 ns, and preferably around 100 ns or less. The switch may be capable of switching voltages of slightly more than half, but less than the entire voltage needed to produce laser pulses of desired energies, and a voltage doubling circuit may be used to produce the voltage required to produce the desired output pulse energies. An oscillator-amplifier configuration may be used, wherein an oscillator switch may be capable of switching voltages less than the entire voltage needed to produce the desired laser pulse energies, while the amplifier amplifies the pulses to the desired pulse energies.

Design of inductive p-i-n diode matching for optical receivers with increased bit-rate operation

Abstract: We have studied matching of a p-i-n photodiode (PD) with a single serial inductive element for broadband operation. The bit rate and rise time may be significantly improved, compared to a device without inductor for nonreturn-to-zero (NRZ) modulation. The matched device offers improved pulse equalization leading to increased receiver sensitivity, and reduces the need for an additional pulse-equalizing filter. The material is presented so that it can serve as a guideline of how the inductor can be included when choosing the thickness of the absorption layer and/or area for a p-i-n PD design, and ends with typical design examples.

Study of a fast, high-impedance, high-voltage pulse divider

Abstract: A novel two-tube, two-stage, self-compensating resistive voltage divider with minimized stray capacitance using copper sulphate solution was explored to measure a fast high-impulse voltage output from a cable Blumlein generator. Self-compensation of the probe was achieved by matching the RC time constant in the two dividing stages. Stray capacitance of the probe was minimized by electric field contouring and matching methods. Experiments were carried out to investigate the probe responses as affected by self-capacitance, impedance, and stray capacitance. Calibration of the optimized probe showed a rise time of 15 ns at a load impedance of 8.68 kΩ with a hold-off voltage of 600 kV.

Method to increase head voltage swing and to reduce the rise time of write driver

Abstract: A voltage-mode boosting write driver circuit ( 40 ) having a pair of voltage boosting PMOS transistor sets ( 44, 46 ) coupled to a high current H-switch ( 42 ). One set ( 44 ) of the boosting PMOS transistors correspondingly pulls output pin HY high, while the other transistor set ( 46 ) correspondingly pulls output pin HX high and the other output pin HY low thereby significantly improving the head voltage swing, and also achieving a faster slew rate. Moreover, resistors (R 3 , R 4 ) of the H-switch are both matched to each other and impedance matched to a flex cable (T 0 ) interconnection impedance, which interconnection is coupled to the thin film head, to thereby eliminate signal reflection such that the write current (Iw) settles quickly with minimum ringing to achieve a high data rate. Moreover, less power dissipation and smaller number of devices used are achieved by making use of existing transient currents of the pre-driver emitter follower stage.

Design considerations and loss analysis of zero-voltage switching boost converter

Abstract: A novel zero-voltage switching (ZVS) boost converter for medium- and high-power applications is proposed. Compared to conventional hard switching boost converters, the switching losses are decreased by a factor of 3 to 4. A design procedure is proposed, based on the minimisation of the total losses in the switch. It is shown that variations of operating frequency, turn-off current and voltage rise time do not affect the control algorithm or the design procedure, even for a wide range of loading conditions and input voltage. A 3 kW prototype using IGBTs is simulated (PSPICE) and developed. The efficiency obtained is more than 90% for load values higher than 20% of full load, and attains 95% for full load. Advantages of the circuit include zero-voltage-zero-current turn-on and zero-voltage turn-off for a wide range of line voltage and load; switching conditions do not depend on the load. The reliable control strategy makes the proposed ZVS boost converter attractive for medium-power applications where IGBTs are used predominantly.

Space and time resolved surface temperature distributions in Si power diodes operating under self-heating conditions

Abstract: In order to optimize and improve the design of power devices with improved surge current safe operating area it is necessary to obtain a good correlation between measured and simulated space and time resolved temperature distributions. Therefore, an IR microscope capable of measuring the space and time resolved surface temperature distributions in Si power diodes operating under self-heating conditions has been developed. The minimum detectable spot size is 15 μm, while the signal rise time is detector limited to about 1 μs. The lower temperature detectivity limit is about 10°C over room temperature. Using this instrument dynamic thermal phenomena in fast recovery 3.3 kV Si power diodes having radiation-induced recombination centers [Proceedings of the 7th EPE, Trondheim, 1997] subjected to 1.2 ms 400–2000 A/cm 2 and 0.3–2 ms 2000 A/cm 2 current pulses have been studied. The experimental results have been compared to results from 2D device simulations including surface recombination and carrier lifetime temperature dependence. The agreement between experimental and device simulation results (i.e. dynamic IV characteristics and time and space resolved temperature distributions) is very good up to a peak current density of 1500 A/cm 2 , and a reasonable good one for peak current densities up to 2000 A/cm 2 (1.2 ms current pulses).

Multi-value voltage-to-voltage converter using a mutli-stage symmetrical charge pump for on-chip EEPROM programming

Abstract: A fully integrated multi-stage symmetrical structure chargepump and its application to a multi-value voltage-to-voltage converterfor on-chip EEPROM programming are presented. The multi-valuevoltage-to-voltage converter is designed to offer two output voltages,power supply and triple power supply alternatively, which is neededfor a memory array. A dynamic analysis of the multi-stage symmetricalstructure charge pump and an optimization design in terms of circuitarea are also given. The circuit is implemented in a 1.2 μ CMOSprocess and the measurement results show that a voltage pulse as shortas 5 μs with a rise time of 3 μs is obtained. For a 5 V powersupply and with a resistive charge of 100 kΩ, the programmingoutput voltage can reach as high as 11 V and output current forprogramming is over 110 μA, which are high enough to program thememory cell.

Simulation and measurement of pulse height and rise-time for electron signals in CZT detectors:: influence of material and electronics parameters

Abstract: A model for simulation of amplitude vs. rise-time biparametric spectra as a function of CZT materials properties was developed. This model takes into account the physical properties of the CZT detectors, the electric field profile and the physics of γ- ray interaction with CZT. The model has been refined to include the filtering effects of the front-end electronics and applied again to biparametric spectra. The electronic filtering is represented by a combination of linear band pass filters. The rise-time measurement circuit induces a non-linearity that is taken into account. A comparison between the electronics simulations and calibration measurements on the actual circuits is presented. In addition, physical and electrical properties of several CZT samples have been characterized and these properties have been incorporated in the model so that actual and simulated biparametric spectra can be compared. Finally, the model is applied to show the influence of the main physical parameters (mobility and lifetime) and of the applied electric field on the biparametric spectra.

Ion mass and scaling effects in PIII simulation

Abstract: Simulation of plasma immersion ion implantation (PIII) is a necessary and valid tool to optimise the treatment homogeneity by adjusting parameters like voltage, plasma density, pulse rise time or pulse length. It can be shown that the ion mass mi and pulse rise time tr are not two independent parameters. Instead, for sufficiently long pulses, when the plasma sheath reaches the stationary state, the dose distributions obtained are characterised by the quotient t r / m i . Therefore, for lower ion masses, shorter rise times must be used to obtain the same relative range distribution. The spatial homogeneity is not affected as the natural scaling length, the initial matrix sheath thickness xini, depends only on the voltage and ion density and is independent of the ion mass. In this report two-dimensional particle-in-cell (PIC) simulations for PIII treatment of trench structures with different t r / m i ratios are presented, encompassing the range of mi=4–131 (corresponding to He+–Xe+), at a pulse rise time of 0.5 μs and a pulse voltage of −45 kV. The implantation profiles are shifted more to the surface for lower masses, as their relative rise time is longer.

A constant slew rate Ethernet line driver

Abstract: An analog bias circuit consisting of two transistors, three current sources, and one resistor facilitates the design of an Ethernet line driver. The rise time is insensitive to process variations and temperature variations, Rise-time accuracy is 223 ppm//spl deg/C over a temperature range of 140/spl deg/C. This line driver has been fabricated in 0.35-/spl mu/m CMOS.

Apparatus and method for automatic matching of signaling rise time to fall time

Abstract: A method and apparatus for matching rise time and fall time in two differential signals. The apparatus includes a system that includes an scaled summer, a reference voltage generator, a comparator, and a storage device. The scaled summer receives two input signals and generates an instantaneous scaled sum of the two input signals. The reference voltage generator generating a reference voltage. The comparator compares the scaled summer output signal and the reference voltage and generates a comparison signal. The storage device stores the comparison signal. The stored comparison signal is usable to adjust one of the rise time and the fall time of both of the two input signals to match one of the fall time and the rise time of the two input signals.

Plasma immersion ion implantation experiments with long and short rise time pulses using high voltage hard tube pulser

Abstract: The performances of two high voltage pulse generators using different circuit configurations for the treatment of metals and polymer materials by plasma immersion ion implantation are assessed. Both pulse generators were built in the circuit category of hard tube type which uses a high power tetrode as a fast on–off switch to control the pulse duration. The first pulse generator has a maximum capacity of 60 kV/10 A at a repetition frequency of 700 Hz with a long pulse rise time (of the order of 40 μs) while the second one is able to operate with full voltage and current of 30 kV and 30 A at 1 kHz with a very short pulse rise time (less than 1 μs). It is shown that the better performance of the latter pulser in terms of rise time is due to a different configuration circuit employed in its construction. Target voltage and implantation current from the application of both pulsers to a plasma glow discharge are discussed using a stationary plasma circuit model.

A throttle control algorithm for improving engine response based on the characteristics of electronic-throttle-control actuator

Abstract: A throttle control algorithm which compensates for the delay in manifold filling is proposed. This algorithm takes into account the control characteristics of an electronic-throttle-control actuator and improves the engine output response. The performance of the algorithm was evaluated in terms of rise time of the manifold pressure and duration of switching control. The results showed that the rise time and the duration of switching control was less than about 100 ms.

A two-phase, four and five boosting ratio, charge pump cell for LCD driver

Abstract: In this paper the charge pump is designed to operate at 10 kHz with 100i A loading for LCD-driver in portable equipments. By estimation of the rise time of the Fibonacci-like charge pump, an optimal switching frequency is designed to make an excellent compromise between the rise time and the dynamic power dissipation. The simulating comparison results based on 1.2i m CMOS, p-substrate double-poly double-metal process parameters show that the charge pump has a high pumping speed and a high power efficiency. By some techniques, a new charge pump is proposed which can operate in versatile portable equipments supplied by 1.2 V, 3.3 V or 5 V.

A new technique for compensating the influence of the feedback DAC delay in continuous-time bandpass delta-sigma converters

Abstract: A new technique for the synthesis of continuous time bandpass delta-sigma modulators with maximum gain margin and higher loop delay is presented. This method is based on the pulse shaping of the DAC output signal taking into account the loop delay and rise time. It is only based on discrete time analysis. It will be shown that high values of the loop delay together with high filter gain margin can be reached. The gain margin sensitivity to the real loop delay variation can also be improved if a return-to-zero DAC (RZDAC) is used.

The design of PIDA controller with pre-compensator [for induction motors]

Abstract: In this paper, PIDA (proportional, integral, derivative, acceleration) for high order system control is simulated. The PIDA controller design is suggested by Jung and Dorf and Shunju Manabe. In the Jung and Dorf method, rise time is rapid, but large overshoot occure at the rise time. Using the CDM (coefficient diagram method) of Shunju Manabe, overshoot does not occur, but rise time is very slow. Therefore, in this paper, a pre-Ccmpensator is proposed to improve the Jung and Dorf method for decreasing the overshoot at the rise time. The controller performance was studied by application to an induction motor in this paper.

Method and apparatus for reduced pin count package connection verification

Abstract: A method and apparatus for testing the chip-to-package connectivity of a common I/O of a semiconductor chip is disclosed which uses reduced pin count testing methods. The method includes driving a test signal transition onto a control pad of a semiconductor chip with a weak driver and comparing the transition rise time with a threshold value. For an I/O with a faulty chip-to-package connection, the rise time is much faster than for an I/O with a completed chip-to-package connection. Additional impedances may also be added to the tester fixturing to increase the sensitivity of the test equipment to the capacitance of the I/O connections.

A compact square waveform 15 kJ generator: 15 ns risetime, 7.5 /spl Omega/ load impedance and 100-500 ns pulse width

Abstract: This paper describes a compact six stage-Marx generator intended to provide the power conditioning for advanced radio frequency (RF) and high-power microwave sources, The generator specifications, which made this system unique, called for relatively high output pulses of energy of 15 kJ across the load impedance of 7.5 /spl Omega/. The charging voltage is organized to vary from 25 to 100 kV. With the matching (dummy) load of 7.5 /spl Omega/ used, the maximum output voltage should be 300 kV, the maximum output current 40 kA and the peak power 12 GW. Without application of the crowbar switch, the pulse width is 0.82 /spl mu/s. A 10 to 90% rise time of about 20 ns was obtained by recording the voltage across the load with a resistive voltage divider probe. When the pulse is observed with a capacitive probe, the rise time falls closer to the value of 10 ns. Three examples of the application of the system to achieve a powerful RF source are given.

A model with nonzero rise time for AE signals

Abstract: Acoustic emission (AE) signals are conventionally modelled as damped or decaying sinusoidal functions. A major drawback of this model is its negligible or zero rise time. This paper proposes an alternative model, which provides for the rising part of the signal without sacrificing the analytical tractability and simplicity of the conventional model. Signals obtained from the proposed model through computer programs are illustrated for demonstrating their parity with actual AE signals. Analytic expressions for the time-domain parameters, viz., peak amplitude and rise time used in conventional AE signal analysis, are also derived. The model is believed to be also of use in modelling the output signal of any transducer that has finite rise time and fall time.

Influence of beam head effects on high-power klystron amplifier

Abstract: Transient behavior of the cavity excitation caused by beam head effects in high-power klystrons is investigated. Recognizing that the input cavity in a klystron can be excited by the input microwave signal and the head of the electron beam, it is shown that the frequency of the induced cavity voltage Vs driven by the signal is the same as the signal frequency ωs. On the other hand, the frequency of the induced cavity voltage Vh driven by the beam head is the cavity resonance frequency ω0. An expression of the induced voltage Vh is obtained by making use of the Laplace transformation. The induced voltage Vh caused by the beam head is expressed in terms of the current-change profile in time. The magnitude of the induced voltage caused by the beam head is inversely proportional to the beam rise time, thereby decreasing drastically for a large value of the beam rise time. It is also shown that the beam head effects are completely negligible whenever the beam rise time τr satisfies ω0τr=2nπ where n is an integ...

DRIVING METHOD AND DEVICE OF GaN BASED SEMICONDUCTOR LASER

Abstract: PROBLEM TO BE SOLVED: To reduce EL light generated by a bias current while an original pulse current for driving is not applied when a GaN based semiconductor laser is driven by the pulse current. SOLUTION: When the GaN based semiconductor laser 20 is driven by the pulse current Ep, a pulse bias current Eb which continues from at least a time before the rise time of the pulse current Ep until the fall time is applied to the semiconductor laser 20, synchronously with the pulse current Ep.