Showing papers on "Rise time published in 1979"

High‐speed InP optoelectronic switch

Abstract: The successful fabrication and demonstration of an InP optoelectronic switch is reported. The results obtained suggest that this device may be better suited for high‐speed analog signal processing applications than previously reported Si and GaAs switches. In experiments using cw mode‐locked lasers, the switches have exhibited an on‐state impedance of 45 Ω for 40pJ of incident laser energy and an inherent rise time of 30 psec. In addition, the switches have been used to generate a train of 70‐psec‐wide pulses at a 900‐MHz repetition rate, and to sample a 68.9‐MHz sine wave at 275 MS/sec with an accuracy to 0.2 dB (98%) and an on‐off ratio of 40 dB.

Pulse switching for high energy lasers

Abstract: A saturable inductor switch for compressing the width and sharpening the rise time of high voltage pulses from a relatively slow rise time, high voltage generator to an electric discharge gas laser (EDGL). The switch also provides a capability for efficient energy transfer from a high impedance primary source to an intermediate low impedance laser discharge network. More specifically, a saturable inductor switch is positioned with respect to a capacitive storage device, such as a coaxial cable, so that when a charge build-up in the storage device reaches a predetermined level, saturation of the switch inductor releases or switches energy stored in the capacitive storage device to the EDGL. Also disclosed are cascaded saturable inductor switches for providing output pulses having rise times of less than ten nanoseconds as required for efficient excitation of EDGL's, the pulse rise time being determined by the thickness of a high permeability material forming the saturable inductor switch. In addition, a technique for magnetically biasing the saturable inductor switch is disclosed so that only pulses from a pulse generator having one polarity are passed and pulses having the other polarity are blocked, thereby improving the lifetime of electrical components that are sensitive to voltage reversals.

Print hammer drive circuit with compensation for voltage variation

Abstract: A print hammer drive circuit is driven by a voltage supply having inherent voltage variations. The driving current is applied to the print hammer coil and the level of the current in the coil detected. After the level of the current in the coil reaches a predetermined maximum level a timing circuit is initiated to control the duration of application of maximum current. Variations in supply voltage on the duration and force of strike of the print hammer have greatly reduced since all timing is based relative to the time that the predetermined drive current level is achieved as distinguished from timing which includes the rise time of the driving current wave form. Also the effects of variations in inductance from coil to coil can be compensated for by adjustment of the timing circuit.

A superconducting sampler for Josephson logic circuits

Abstract: A method is described for automating a technique which is used to sample transition duration (rise time) in superconducting logic circuits. The method is based on measuring the time at which a biased Josephson junction switches under the influence of an applied signal. The system transition duration is limited primarily by time jitter which is estimated to be 7 ps. Transition durations of as little as 9 ps have been observed.

Memory circuit with increased operating speed

Abstract: Digit lines, connected to the input and output terminals of a memory cell composed of MISFETs, are coupled to common data lines through a switching circuit which is controlled by a decoder circuit. There is also connected with the digit lines a load which is composed of a plurality of enhancement mode MISFETs connected in series in the diode form. The high level of the signals at the digit lines is lowered by the action of the load means. In response to the reduction in the potentials at the digit lines, the switching means is rendered conductive at an early rise time of control signals. As a result, the operating speed of the memory circuit can be increased.

A 1 Gbit/s integrated optical modulator

Abstract: A waveguide directional coupler modulator is demonstrated with a bandwidth of 1 GHz and a rise time of 590 ps. An analysis of the electrical parasitics is presented and the device response is found to be transit-time limited. The scaling of the frequency response is shown to be characterized by a bandwidth-length product of 1.1 GHz - cm.

Thin film superconducting switches

Abstract: Although thin superconducting films have been suggested for use in switching electrical power, virtually no experimental work has been reported. Our present research investigates thin films switched by applying a fast pulse of magnetic field perpendicular to the plane of the film. Short sections of niobium films, carrying approximately half of their critical current, were switched completely into the normal state upon application of pulsed fields as low as 0.02 T (200 gauss). The field pulse has a rise time and length of order 10 μsec, but switching was more rapid. It is shown that the magnitude of the field, and not its rise time, cause the switching. Recovery times, upon removing the current source, were also of order 10 μsec.

Transient conductivity measurements with subnanosecond time resolution.

Abstract: The parameters governing the response time of a system to follow transient changes of conductivity caused by short pulses of radiation are discussed, and designs for coaxial conductivity cells with parallel‐plate electrodes to obtain subnanosecond time resolution are described. The performance of the system is evaluated using ionization pulses of 30‐ps width. This yields values in agreement with theory: 95 ps for the rise time and 80 ps for the fall time with virtually no signal distortion. Ways to decrease these times further are discussed.

Pulsed DC constant current magnetic flowmeter

Abstract: A magnetic flowmeter includes a coil driving circuit which controls both the maximum, steady state current and the current rise time through the coils and makes them independent of the inductance of the particular coil being driven. The maximum current is set by a reference voltage derived from a common source with a second reference voltage utilized in the signal processing chain. The ratio of these reference voltages therefore remains constant and the output signal is independent of the absolute value of the common source of the two reference voltages.

Music selector of tape recorders

Abstract: PURPOSE:To perform selection of desired musics within a short time by setting an FF by delaying the head detection signal of information signal, resetting the same by the final end detection signal and changing over the reproduction to constant speed and high speed by the output thereof. CONSTITUTION:An FF 7 sets at the fall time t0 of the output signal (b) of an integrator 6 and the output signal (c) thereof is supplied to an integrator 9 and counter circuit 10. The signal gradually levelling up from the time t0 is drawn out from the integrator 9 and is supplied to the FF7 by way of an FF 8 and delay circuit 11. On the other hand, the counter circuit 10 supplies the signal (f) driven at the rise time t0 of the output signal (c) of the FF 7 to a counter 12 so that the ''1'' signifying the reproduction of the first music is displayed. The FF 8 is set at 10 seconds from the rise time t0 of the output signal (d) of the integrator 9 and the signal (e) thereof is inputted to a mechanism driving circuit 13, which is then changed from constant speed reproduction to fast feed state from the time t1, thus the FF7 enters the constant reproduction standby for the second music. Thereby, the desired music is selected within a short time.

A model for the on state of amorphous chalcogenide threshold switches

Abstract: A detailed isothermal model of the on state of amorphous chalcogenide threshold switches is developed. Steady‐state carrier generation and recombination processes are discussed and estimated, and the carrier distributions in the radial direction of the conducting filament are calculated under the assumption that there are no axial variations. Simulations of dynamic decay of the filament after the sustaining voltage is removed are used to calculate both the maximum interruption time before reswitching is necessary and the time dependence of the device resistance during decay as functions of the on‐state operating point. Good agreement with experiment is obtained. The model predicts a rapid increase of device resistance in the vicinity of the maximum interruption time, and this has been confirmed by subsequent measurements. Since the rise time of the device resistance in this region is limited by the measuring circuitry and essentially independent of the on‐state operating point up to at least 100 mA, the e...

Characteristics of Co-Axial Marx Generator and Its Application to Electron Beam Fusion

Abstract: A co-axial Marx generator with a short rise time of pulse less than 4 nsec, and ~40 nsec flat top duration was successfully constructed. For the attainment of electron beam fusion, the requirements for the beam source are a rise time of less than 1 nsec, an impedance of less than 0.01 Ω and an inductance of less than several nH/MV. The co-axial Marx generator can be considered to be the most important tool for these purposes. We analyzed this rectangular output pulse of the co-axial Marx generator and applied it to electron beam fusion.

A cryogenic microwave switch

Abstract: A cryogenic microwave switch has been developed which has an isolation greater than 70 db, a throughput of 0.99, and a rise time of a few nanoseconds. The switch consists of an H-plane T in which one arm contains a short and a sapphire tube containing He. The short is fixed so as to isolate the other two arms when the He is not excited. The high degree of isolation is a direct consequence of the superconducting properties of the waveguide. The tube of He is located a quarter guide wavelength from the T so that when a plasma discharge is created in it, the other two arms become tightly coupled. Plasma rise times of order several nanoseconds have been achieved by applying a high voltage dc pulse across the tube. The switch has been used to release microwave energy stored in a superconducting resonator, creating high power microwave pulses. Here we will discuss the design parameters of the switch and its observed performance.

High repetition rate burst-mode spark gap

Abstract: Results are presented on the design and testing of a pressurized gas blown spark-gap switch capable of high repetition rates in a burst mode of operation. The switch parameters which have been achieved are as follows: 220 kV, 42 kA, a five-pulse burst at 1 kHz, 12-ns rise time, 2-ns jitter at a pulsewidth of 50 ns.

Time-resolved resistance during spark gap breakdown

Abstract: The breakdown voltage and the time derivative of the current through a spark gap terminating a transmission line were measured as a function of 4 gas species, 3 gap pressures, and 2 gap spacings. From these measurements, the time-varying channel resistance, the power, and the energy dissipated in the discharge can be determined for the first 1500 ps of breakdown. Data were obtained with a 74-cm-long transmission line, open at the charging end, and terminated by a spark gap at the other end. The line was pulse charged with a 2-µs rise time pulse having a maximum voltage of 3 kV. The breakdown voltage was determined by monitoring the charge voltage waveform while a di/dt probe close to the spark gap provided a sampling oscilloscope with the other desired signal. The latter waveform was then digitized and the data were reconstructed using Fourier techniques on a computer to account for the frequency response of the required signal delay line.

Short circuit protection circuit

Abstract: A protection circuit is provided in which the output voltage is sensed and the output device is shut-off for protection when the output voltage falls below a predetermined trip voltage. The monolithic integrated circuit includes a voltage shifting circuit for transferring the output voltage to a biasing circuit which biases a switching circuit which turns the line driver off, when an overload or short circuit causes a voltage drop below a predetermined trip voltage. The protection circuit is disabled during start-up or signal rise time by splitting the input signal into two separate paths in which the signals have different delays. The shorter delay allowing the input signal to rise and to appear on the output line before the longer delay input signal rises enabling the protection circuit.

Measurement of time delay

Abstract: PURPOSE: To conduct the measurement with less error, by determining position of a crossing point between an input signal and an output signal on an oscilloscope picture and also by calculating time delay from a measurement value of frequency of the output signal using a counter. CONSTITUTION: An oscillator 4 which generates variable-frequency pulses is connected to an input terminal 2 of a device 1 to be measured, the frequency counter 7 is connected to an output terminal 3, and the oscilloscope 5 is connected between the input terminal 2 and the output terminal 3. And by varying the oscillation frequency of the oscillator 4, it is indicated on the oscilloscope picture that a point of 1/2 amplitude at the input signal rise time coincides with a point of 1/2 amplitude at the output signal fall time. And then, under this condition, the frequency is measured by the counter 7 to calculate the time delay. And therefore, it is possible to prevent introduction of measurement error even at the time of a large time delay and also to conduct the measurement with less error. COPYRIGHT: (C)1981,JPO&Japio

One Nanosecond Pulsed Electron Gun Systems

Abstract: At SLAC there has been a continuous need for the injection of very short bunches of electrons into the accelerator. Several time-of-flight experiments have used bursts of short pulses during a normal 1.6 micro-second rf acceleration period. Single bunch beam loading experiments made use of a short pulse injection system which included high power transverse beam chopping equipment. Until the equipment described in this paper came on line, the basic grid-controlled gun pulse was limited to a rise time of 7 nanoseconds and a pulse width of 10 nanoseconds. The system described here has a grid-controlled rise time of less than 500 pico-seconds, and a minimum pulse width of less than 1 nanosecond. Pulse burst repetition rate has been demonstrated above 20 MHz during a 1.6 microsecond rf accelerating period. The order-of-magnitude increase in gun grid switching speed comes from a new gun design which minimizes lead inductance and stray capacitance, and also increases gun grid transconductance. These gun improvements coupled with a newly designed fast pulser mounted directly within the gun envelope make possible subnanosecond pulsing of the gun.

Feedback‐stabilized fractional fringe laser interferometer for plasma density measurements

Abstract: A feedback stabilization technique is described for a fractional fringe interferometer measuring plasma electron densities. Using this technique, a CO2 laser Michelson interferometer with a pyroelectric detector exhibited a sensitivity of 3.4×10−4 fringe on a 1‐ms time scale and, due to acoustic pickup, 1.8×10−2 fringe on a 10‐ms time scale. The rise time is 45 μs. Stabilization against slow drifts in mirror distances is achieved by an electromechanically translated mirror driven by a servo system having a 0.2‐s response time. A mechanical chopper in one of the two beam paths generates the signal which drives the servo system.

Ternary converter circuit

Abstract: PURPOSE:To improve the rise time of the output voltage for the circuit which converts the high voltage input to the low voltage output and obtains three output states, by connecting in parallel the FET series circuits which receive application of the back gate bias and complements the output current of IG-FET.

Semiconductor memory unit

Abstract: PURPOSE:To ensure generation of the initial setting signals with no limitation due to the scale of the rise time of the power voltage by using the output signals of the monostable multivibrator as the initial setting signals. CONSTITUTION:Power voltage 11 of power supply device 1 begins to rise at time t0 and then applied to the ''1'' input of monostable multivibrator 300 at time t1 via resistance 301. And when the voltage exceeds the threshold level, the ''0'' level of pulse duration tw determined by the product of resistance 303 and capacitor 302 is delivered from the output of Q in the form of initial setting signal 3041. In this case the levels of 303 and 302 are set to the value at which output pulse duration tw of 300 becomes larger than rise time tr3 of voltage 11. The oscillation of oscillator circuit 21 is inhibited although voltage 11 irses completely at time t2 since signal 3041 is at the ''0'' level until time t3. And NAND gate 211 opens when signal 3041 becomes at the ''1'' level. Thus, circuit 21 starts oscillation in a fixed period. In such way, the initial setting signals can be generated within the semiconductor device with less number of the circuit.

Circuit for preventing reverse rotation of ignition means of internal combustion engine

Abstract: PURPOSE:To prevent reverse rotation effectively, by keeping a transistor in conduction before it reaches the peak rise time of voltage from the time when a self-shortcircuiting regulator is set into actuation, and thereby increasing the conduction width of the transistor. CONSTITUTION:Voltage of a charge coil 1 is impressed to the base of a transistor 11 via a diode 19 and a resistance 20. Here, since the transistor 11 can be energized also by the plus voltage of charge coil 1, the conduction width of transistor 11 is increased toward the opposite side of an ignition signal at the time of normal rotation, so that operation is carried out normally in this state. At the time of reverse rotation, however, the conduction time of transistor 11 is increased since it is energized by the charged voltage and an advancing ignition signal can be also shortcircuited. Therefore, it is enabled to cause misfiring without fail at the time of reverse rotation within an operable range of a pulser.

Logical operation unit

Abstract: PURPOSE:To reduce the noise generated at the leading edge and the trailing edge of signals outputted from a logical operation circuit, by delaying the input of each logical operation circuit in order by minute time and generating the rise time and the breaking time longer than the regular rise time and breaking time of signals in appearance. CONSTITUTION:Logical operation circuit 1 is constituted by n-number logical operation circuits 2, (n-1)-number delay elements 3 and control circuit 6 which controls the output signal level of each circuit 2 to 1/n of the regular level, and the input of each circuit 2 is inputted while being delayed in order by a minute time according as the operation of circuits 2 is moved from the left to the right by elements 3. Therefore, when circuit 2 is driven, the rise time and the breaking time longer, in appearance, than egular rise time and breaking time of output signals outputted onto signal line 4 are generated, and signals having the same level as regular output signals are synthesized and outputted. As a result, the noise generated at the leading edge and the trailing edge of output signals of circuit 2 can be reduced.

Characterization of light emission from amorphous chalcogenide switches

Abstract: Narrow‐bandwidth infrared radiation has been detected from amorphous As50Te50 threshold switches in the ’’on’’ state of thin parallel plane devices which possess optical feedback. The radiation has a fast rise time and is dependent on a minimum threshold ’’on’’ current which is independent of device area. The radiation output is substantially independent of device temperature and is thus not thermally activated. The output is not observed in heterojunction devices which have little optical feedback.

Electric power unit of nuclear fusion system

Abstract: PURPOSE:To maintain the balanced position of plasma by connecting in series the energy storage coil and the thyristor rectifier unit and adjusting accurately the voltage applied to the position control coil. CONSTITUTION:For plasma current rise time, switch 23 is opened. This allows the sum of voltage of the second high voltage generator 11 and the voltage of thyristor rectifier 19 to apply to the phase control coil 10 through diode 16, variable reactor 17 and variable resistance 18. The current detectors 24 and 25 detect respectively plasma current at a plasma current rise time and the current of position control coil 10, the detecting signal of which is entered into the controller 20, and thyristor rectifier 19 is controlled by controller 20.

Modified SCR for optically actuated triggering.

Abstract: A simple inexpensive, optically actuated triggering device (optical trigger) has been developed for synchronizing pulsed lasers with signal gathering instrumentation. The heart of this device is a commercially available SCR that has been modified for light activated operation. The optical trigger delivers, into a 50‐Ω load, a pulse of either 84 V with a 8.3‐ns rise time and 3.5‐μs width, or 42 V with a 6.2‐ns rise time and 7‐μs width. The device is sensitive throughout the visible and near‐visible spectrum. It has a transit time of only 2.2 ns and less than 1‐ns jitter. The performance of this optical trigger is examined in terms of the criteria of an ’’ideal’’ optical trigger and the effects of circuit and input parameters on output pulse characteristics are discussed.

Luminous element driving circuit

Abstract: PURPOSE:To improve rise time and fall time of photooutput wave in intensity modulation time of a luminous element, by providing a spike generation circuit between a photo communication luminous element and a transistor which drives the element CONSTITUTION:When connecting a luminous element 38 with a luminous element driving transistor 36 having an input terminal 31, a spike generation circuit 34 is interlaid between them This circuit 34, which is composed of a resistor 32 having a required resistance value and a capacitor 33 and also a coil 37, connects the resistance 32 to the cpapacitor 33 in series, and a circuit in which the coil 37 and the element 38 are connected with each other in parallel is connected to the circuit 34 Further, the resistor 32 and the element 38 are grounded, a collector of the transistor 35 is connected to the junction point between the capacitor 33 and the coil 37, and voltage -VBB is impressed onto an emitter through the resistor 36 It is possible, in this manner, to largely improve rise time and fall time of photoinput wave of the element