Showing papers on "Rise time published in 1981"

Technical aspects of brainstem evoked potential audiometry using tones.

Abstract: The brainstem response to brief tones contains a large vertex-positive component If high-pass filter settings above 20 Hz are used, particularly with high rolloff slopes, the morphology of the response changes so that a vertex-negative wave becomes the most prominent component of the response The amplitude of the response is unaffected by stimulus presentation rates of up to 35/sec Tones with longer rise times have greater frequency specificity, but at rise times of greater than 5 msec, the brainstem response becomes very small At high intensities, regardless of the rise time, the response to tones is not completely frequency specific, and notched noise masking should be used to obtain frequency-specific responses

Impedance of the amphibian lens.

Abstract: 1 The electrical resistance of the perfused frog lens was measured using separate internal current passing and voltage measuring electrodes 2 The resistance values obtained using voltage clamp and direct and alternating current techniques were in good agreement 3 The voltage transients induced in response to current steps were multi-exponential in form Increasing the external K concentration reduced both the amplitude of the voltage response and the rise time 4 The impedance characteristics were investigated in more detail using alternating current analysis techniques 5 In an equivalent-circuit modelling study it was assumed that there were two major pathways for current flow in the lens The first through the surface membranes and the second through the inner fibre membranes via the narrow extracellular spaces 6 The experimental impedance loci could not be adequately fitted by a simple two time constant model and a third time constant was introduced which may represent diffusion polarization effects in the extracellular spaces 7 The three time constant model gave good and consistent fits to impedance data from a number of preparations 8 The form of the impedance loci was also dependent on the external K concentration, but the only fitted parameter which changed consistently with external K was the surface membrane resistance (Rs)

Characterization of In 0.53 Ga 0.47 As photodiodes exhibiting low dark current and low junction capacitance

Abstract: The preparation and properties of grown p-n homojunction In 0.53 Ga 0.47 As photodiodes for operation in the 1-1.7 \mu m wavelength range are described. At a reverse bias of 20 V, these diodes exhibit generation-recombination limited dark current as low as 2 \times 10^{-9} A, junction capacitance of 0.3 pF, and pulse response corresponding to a circuit-limited rise time of 60 ps and diffusion-limited full width (FWHM) of 140 ps.

Apparatus with nanosecond field transition times for field reversal studies of surface processes at high temperatures

Abstract: A new type of field‐reversal apparatus is described. It is intended for desorption and surface reaction studies in systems with surface ionization. The problems of mechanically modulating the molecular beam are circumvented by instead reversing the electric field outside the surface and thus perturbing the steady‐state desorption conditions. The short field reversal time of ⩽ 10 ns with a 90 V voltage step is reached by using VMOS transistors with optoisolated driving circuits. The ions from the ionizing surface are converted to electrons on a Cu–Be dynode. The electrons give photons in a scintillator, and the photons are detected by a photomultiplier outside the vacuum wall. The apparatus dependent signal rise time is around 40 ns, which means that surface processes with very short characteristic time constants can be measurable.

GaAs Fet Ultrabroad-Band Amplifiers for Gbit/s Data Rate Systems

Abstract: A novel ultrabroad-band amplifier configuration suitable for GaAs FET's has been developed. The developed amplifier circuit operates as a capacitor-resistor ( C-R ) coupled mnpfifier circuit in the low-frequency range in which |S/sub 21/| for the GaAs FET's is constant. It also operates as a lossless impedance matching circuit in the microwave frequency range in which |S/sub 21/| for the GaAs FET has a slop of approximately -6 dB/octave. Using this configuration technique, 800-kHz 9.5-GHz band (13.5 octaves), 8.6-dB gain GaAs FET amplifier modules have been realized. The amplifier module has 40-ps step response rise time. It also has low input and output VSWR. By cascading two-amplifier modules, 19-dB gain over the 800-kHz to 8.5-GHz range and 50-ps step response rise time were obtained. NF is lower than 8 dB over the 50-MHz to 6-GHz range.

ZnO varistors for protection against nuclear electromagnetic pulses

Abstract: The use of ZnO‐based metal‐oxide‐varistor materials in a transient protection device for communications circuits against the effects of nuclear electromagnetic pulses (NEMP) is discussed. The guidelines for such devices call for subnanosecond response time to NEMP and an insertion loss of less than 0.4 dB at 100 MHz. We have measured the response of varistor materials to ∼500‐ps rise time pulses of various amplitudes and durations. No varistor ’’turn on’’ time is evident in these data indicating that the initiation of the highly nonlinear conduction process takes place in less than 5×10−10 s. The insertion loss is calculated from the known high‐frequency electrical properties and found to agree quite closely with the experimentally determined value of 0.1 dB at 100 MHz for varistor chips of cross section 0.025×0.025 cm and thickness 0.01 cm. A packaging configuration for these chips is also described. We conclude that ZnO varistors have application in an NEMP protective device.

Signal Shaping and Tail Cancellation for Gas Proportional Detectors at High Counting Rates

Abstract: A low noise, wide bandwidth preamplifier and signal processing filter were developed for high counting rate proportional counters The filter consists of an eight pole Gaussian integrator with symmetrical weighting function and continuously variable shaping time, ?s, of 8 ns to 50 ns (FWHM) preceded by a second order pole/zero circuit which cancels the long (1/t) tails of the chamber signals The preamplifier is an optimized common base input design with 2 nsec rise time and an equivalent noise input charge of < 2000 rms electrons, when connected to a chamber with 10 pF capacitance and at a filtering time, ?s, of 10 ns

Voltage and time characteristics of the potassium mechanoreceptor current in the ciliateStylonychia

Abstract: 1. The membrane current underlying the hyperpolarizing receptor response following a mechanical stimulus to the cell posterior of the hypotriche ciliateStylonychia mytilus was investigated with a two microelectrode voltage-clamp technique. 2. The relationship between the amplitude and the time course of the receptor current and the wave form of the voltage pulse driving the mechanical stimulation system was studied (Figs. 2, 3, 4). The amplitude of the receptor current increased approximately linearly with the driving pulse, but both amplitude and time course of the receptor current were unaffected by varying the duration of the driving pulse. 3. The mean maximum amplitude of the receptor current elicited by mechanical stimuli was 20.4 ± 5.6 nA (± S.D., n=19) at the normal resting potential of −51.4±1.6 mV (n=20). This corresponds to an averagemaximum conductance increase of 0.61 μS. The receptor current flow reversed its direction at a membrane potential of −87.7±3.3 mV (n=18; Figs. 5, 6). At the extracellular K+ concentration of 1 mM, the intracellular K+ concentration was calculated to be 33.3 mM. 4. The amplitude of the receptor current changed linearly with the membrane potential in the hyperpolarizing direction. In the depolarizing direction the receptor current amplitude increased less than expected from the increased driving force. The conductance increase following a mechanical stimulus was in average less than 50% at zero mV as compared with that at the normal resting potential of around −50 mV. 5. The receptor current decayed with a single exponential time course, its mean time constant was 7.3±1.2 ms (n=15). The time course of the receptor current changed with the membrane voltage. The rise time and the time constant of decay of the receptor current increased with hyperpolarization towards the reversal potential, and both decreased with depolarization (Figs. 7, 8). These changes with membrane potential were approximately exponential; the voltage displacement to achieve an e-fold increase of the rise time was −410 mV, and of the decay time constant −110 mV. At membrane potentials just beyond the reversal potential both rise time and decay time constant of the receptor current, now flowinginward, were reduced by 20 to 50%, before increasing again with further hyperpolarization (Fig. 9). 6. The results indicate that the life time and possibly the conductance of mechanically activated ionic channels are dependent on the membrane voltage. The implications of these findings for a mechanoreceptor are compared with data obtained at chemoreceptors, e.g. at neuromuscular junctions and other chemical synapses.

Telephone line protection device for steep electromagnetic pulses - uses low pass LC filter with voltage dependent shunt impedances connected symmetrically in series and parallel with grounded chassis

Abstract: Two symmetrical conductors (8,9) link the input terminals (1,2) to respective inductors (14,15) and are connected by spark gaps (10,11) to the earthed screen between the two input stages (3,4). The inductors (14,15) are connected via feed-through insulators (18,19) into an output stage (6) contg. a low-pass filter (24) with 50 Hz cutoff frequency (for power line protection). The normal operating voltage (e.g. 220V) and current (100A) are passed without distortion, but perturbing pulses of higher frequency are greatly attenuated by Zener diode or voltage-dependent resistive shunts (20,21) at the filter input connections. A 10kV peak pulse with 10ns rise time is reduced to less than 100V at 1kV/microsecond at output terminals (33,34). Alternatively the two inductors are replaced by a screened 1:1 isolating transformer.

Parametric study of the 357.7‐nm oscillation in a TE (transversely excited) N2 laser

Abstract: New experimental results on the factors affecting the 357.7‐nm oscillation in a Blumlein‐driven N2 laser are presented and compared with the theoretical considerations. The laser output at 357.7 nm is enhanced not only by adding a foreign gas but also by reducing the amount of preionization, decreasing the repetition rate of discharge, and lowering the inductance of the discharge circuit. On the basis of the assumption that these actions serve to shorten the rise time of discharge current in their common function, such experimental results are explained fairly well.

Surge voltage generator

Abstract: PURPOSE:To enable the independent controlling of rise time and fall time of the surge voltage against a sample by a method wherein charge and discharge resistors to be connected to the base of a transistor forming an emitter follower connection are selectively connected by a switch. CONSTITUTION:A peak value instituting direct current source W is connected to a sample X to be measured like an electronic apparatus, etc., through a transistor T forming an emitter follower connection. A capacitor C2 is connected between the base of the transistor T and the earth, and a voltage rise time instituting charge resistor R2 and a voltage fall time instituting discharge resistor R3 are connected to the base of the transistor T through a switch S. The switch S is made to close to the R2 side to make the rising of voltage, and then is made to close to the R3 side to make the falling of voltage. Therefore the rising time and the falling time of voltage can be instituted notwithstanding the impedance of the sample X to enable the highly precise controlling.

Semiconductor memory core program control circuit

Abstract: A circuit to restrain the rise time of a programming pulse generated in an electrically alterable read-only semiconductor memory in which excessively sudden changes in the pulse are capacitively coupled, through active devices that can be built on the chip, to a grounding switch device so as to periodically drain away the control signal used to create the pulse.

High speed line driver with ground output capability

Abstract: An FET driver circuit is disclosed which provides short circuit protection at the output node without reducing its performance. Grounded short circuit protection is achieved by sharing a load resistance at the output node in two parallel components, a low resistance active FET load and a high resistance active FET load. A delay element is inserted between the data input node and the gate for the low resistance active FET load. When the data input is low, both of the active FET load devices are off and the active logical FET device is on causing a low output value for the circuit. When the data input for the circuit goes high, the output capacitance is initially charged by the high resistance FET load device and is followed after a short delay, by charging through the low resistance FET load device. The low resistance FET load device cuts off current flow automatically after a predetermined period of time transpires. This delay duration is designed to be equal to or greater than the desired output rise time for the circuit, and less than the time required to destroy the low resistance device if it were to have its output terminal grounded. Thus, if the output of the circuit is accidentally shorted to ground, the circuit is protected because the brief on-time of the low resistance device limits power dissipation below destructive levels, and because the short circuit current in the high resistance device is of insufficient magnitude to cause problems.

Test set for transient protection devices

Abstract: A method and device for testing transient protection circuits comprising itive and negative high voltage protection circuits and high voltage fast rise time protection circuits. A bipolar test signal with alternate positive and negative high voltage pulses is applied to the circuit under test. Determination is made whether the pulses are within a predetermined voltage window. Signals indicating pass/fail responsive to that determination are generated. A high voltage fast rise time negative pulse is applied to the circuit under test. Changes in the voltage-time waveform are sensed and compared to predetermined levels. Pass/fail signals are generated in response to the comparison.

Fast microelectrode headstage for voltage clamp

Abstract: Fast response in microelectrode recordings may be made by measuring the current through a microelectrode, rather than the voltage. Current recording keeps the electrode at virtual earth and thus prevents the loss of high frequency response owing to charging of the electrode capacity through the tip resistance. We describe a circuit which is a combination of current and potentiometric recording. For high frequencies the amplifier functions in current mode, and for low frequencies in potentiometric mode so that there is no average load on the cell. The amplifier rise time is less than 5 microseconds, is stable, quiet and requires no high frequency compensation.

Low Pressure Spark Gap

Abstract: : Tests of an experimental low pressure spark gap Blumlein switch are presented. Gas flows from a pulsed valve into the gap at a steady rate through holes in the cathode and results in a steady pressure of about 0.1 Torr. The pressure outside the gap over the Blumelin insulator is much lower. Trigger electrodes are mounted in the grounded cathode. Initially the current rises exponentially with time with rate constant proportional to gas density. Measurements of rise time, jitter and voltage holding recovery time are presented for charge voltages up to 250 kV for variations of charge time, gas density, gas type and triggering method.

Amplitude- and rise-time-compensated filters

Abstract: An amplitude-compensated rise-time-compensated filter for a pulse time-of-occurrence (TOOC) measurement system is disclosed. The filter converts an input pulse, having the characteristics of random amplitudes and random, non-zero rise times, to a bipolar output pulse wherein the output pulse has a zero-crossing time that is independent of the rise time and amplitude of the input pulse. The filter differentiates the input pulse, along the linear leading edge of the input pulse, and subtracts therefrom a pulse fractionally proportional to the input pulse. The filter of the present invention can use discrete circuit components and avoids the use of delay lines.

System for automatically controlling the breakdown voltage limit of an electrofilter

Abstract: A system for automatically controlling the voltage of an electrostatic filter with respect to its breakdown voltage limit. The detection of secondary voltage breakdowns which occur within a post-breakdown time period after an initial voltage breakdown cause the filter voltage to be lowered to zero value. After a deionizing time period, the filter voltage is gradually raised during a predetermined rise time period until it reaches a new value. The duration of the deionizing time period and the rise time period may be advantageously computed in response to the history of voltage breakdowns, by a microcomputer system.

Pulse generating circuit

Abstract: PURPOSE:To generate an optional pulse having long pulse width by a few circuit elements, by connecting in series the resistance function element to the complementary inverter circuit, and connecting the capacity element between the input terminal and the electric power source. CONSTITUTION:The N channel MOSFET 20 operates as the load resistance for detecting a through-current flowing into the complementary MOSFETs 18 and 19. The capacitor 22 sets both the rise time tr and the fall time tf of the signal B which is output from the inverter 16, to the input signal A. And, a signal having the pulse width corresponding to the time tr and tf of the signal B appears at the output terminal 21. Also, the larger the times tr and tf become, the more the through- current (i) is increased and it flows for many hours. One level of the output signal is nearly decided by the ratio of conduction resistance of the transistors 18, 19, 20 in case when they are all conducting.

Simple, reproducible, acoustically transparent pressure transducer with an 18‐ns rise time

Abstract: We describe an inexpensive, unbacked, solid dielectric capacitance‐like pressure transducer and preamplifier. The device has an adjustable sensitivity of about 0.5 μV/Pa into a 50‐Ω load, a geometry‐determined rise time of about 12 ns, and a flat frequency response from a few kHz to its resonant frequency of about 40 MHz. The geometry and method of construction make it simple to calculate response characteristics and it is usable at pressures from 103 Pa to at least 107 Pa.

System for deriving precise instants of triggering of a pulsed device

Abstract: A system for correcting the time of occurrence of a triggering point along the rise time of a pulse, particularly in a DME system comprising interrogator and transponder stations. Actual received pulses which may be distorted by multipath signals or other effects are compared with stored rise time reference values to generate corrections to time correct the triggering point. The correction may be transmitted between interrogator and transponder in coded form.

Glitch preventing circuit of digital-to-analog converter

Abstract: PURPOSE:To prevent the occurrence of a glitch securely by simple constitution, by making the rise time and fall time of a digital output signal coincide with each other by delaying the rise or fall. CONSTITUTION:If a digital signal outputted from digital output device 11 changes from [1, 0, 0...0] to [0, 1, 1...1] at some point, the most significant digit bit MSB changes from [1] to [0] and other bits change from [0] to [1]. While the other bits are still at level [0], MSB has fallen down to level [0], and glitch occurs temporarily to the output of device 11. On the other hand, MSB, while inverted by inverter circuit 12, is delayed and the delay time coincides with the rise time of the other bits. Then, the other bits rise without being delayed by inverter circuit 12, so that the both will coincide mutually.

Apparatus for evaluating performance of oxygen sensor

Abstract: PURPOSE:To enable the evaluation of the performance of an oxygen sensor with the caluculation of a control frequency thereof by continuously measuring rising and falling response times of the sensor while cyclically varying the air- fuel ratio of a combustion gas. CONSTITUTION:According to an air-fuel ratio varying signal S generated from an air-fuel ratio varying signal generator 16, an electromagnetic valve 10 is driven and a combustion gas varies from the lean side to the over rich side. An oxygen sensor 12 (17 and 18) is provided on an exhaust tube 11 of a combustion chamber 5 to control the air-fuel ratio and an output voltage Vs is outputted according to a waveform of an air-fuel ratio varying signal S. The output voltage Vs is inputted into a waveform processor 19 with the air-fuel ratio varying signal S of the air-fuel ratio signal generator 16 to continuously measure the rise time and the fall time of the output voltage Vs over many cycles. From the measured times, a control frequency is calculated to evaluate the performance of the oxygen sensor.

Waveform measuring method and its device

Abstract: PURPOSE:To measure the rise time, fall time and various other times of waveforms without any error by calculating the grade of waveforms from the potential difference and time difference between arbitrary points on the way of the rise and fall of the waveforms. CONSTITUTION:The detection signal of a trapezoidal shape from a detecting part 1 is inputted via an amplifier 2 to comparing parts 3, 4 and a peak holding circuit 5. The outputs of the comparators 2, 3 are inputted to AND gates 6, 7, 8 and a flip- flop circuit 9. Counter parts 11, 12, 13 count the clock pulses from a clock pulse generator 10 while the AND gates 6, 7, 8 are opened. The outputs of the counter parts 11, 12, 13 indicate the time between arbitrary potential differences of the trapezoidal waveform and these are inputted to an arithmetic part 14. In addition, the peak value of the trapezoidal waveform is inputted from the peak holding circuit 5 to an arithmetic part 14 via an A/D converting part 15. The arithmetic part 14 calculates various times of the waveform.

A New Technique for Input Protection Testing

Abstract: Input protection circuits are typically evaluated by resistively discharging a capacitor into the tested device with one or more of its pins grounded. These techniques usually result in junction damage in or near the irnput protection circuit, rather than in gate oxide ruptures as is seen in most electrostatic damage field failures. To eliminate this inconsistency, a new testing technique has been developed. Electro-static failures are modeled as occurring while the affected device is isolated from ground and forced to change potential at an externally determined rate. The nlew technique provides two quantitative parameters, namely the maximum voltage and the rise time of the applied pulse, which yield the voltage slew rate and the power dissipated into the device. By adjusting these paramieters to obtain a predeterrnined failure rate, an accurate comparison of the input protection networks on different devices may be obtained. In addition to reproducing the field failure mechanism, experimiiental data indicates that this technique has sufficient sensitivity to detect slight design variations in almiiost identical input protection circuits.

Optical fiber fusion splicing method

Abstract: A method for fusion-splicing aligned optical fibers using heat generated by gas discharge produced between electrodes which are energized by an AC voltage. At first, a high trigger voltage is applied across the electrodes to generate the discharge, after which an AC voltage lower than the trigger voltage is applied across the electrodes to produce steady-state discharge. The AC voltage is selected to satisfy the relation, 10tO ≧(tf +td +tr), where tO is the time necessary for ions created by the discharge to flow from one of the electrodes to the other and tf, td and tr are the fall time, the quiescent time and the rise time of the AC voltage. Alternatively, a sine-wave AC voltage is used having a frequency higher than 500 Hz.

Tone signal detection circuit of radio communication equipment

Abstract: PURPOSE:To quicken a rise time by greatly shifting the center frequency of the electronic variable tone filter to the low pass side by connecting a capacitor. CONSTITUTION:When a tone signal is led into the electronic variable tone filter 1, one of Rr-Rx is selected in order by the code selector 8, it is connected in parallel to the resistor R13, and a tone signal of its preamble and code is made to pass through. A tone signal which has passed through the filter 1 is sent to the level detection circuit 2 and the zero-crossing detection circuit 3. The circuit 3 leads in a part of the tone signal from the circuit 2, too, as a comparison signal, and sends out a zero-crossing signal. This sinal is sent to the gate circuit 5, and the circuit 5 generates an output at the time of zero-crossing after the tone signal has been counted by 4 waves by the counting circuit 4. A part of its output is sent to the timer 6 as a reset signal, and the timer 6 sends a reset signal to the circuit 4 after a prescribed time has elapsed, and cuts off a gate signal from the circuit 4. As a result, the switching circuit Se is turned on, and the capacitor Ce is connected in parallel to the OP amplifier Q3.

Circuit switching analysis for optically excited metal-insulator (tunnel)-silicon thyristor (MIST)

Abstract: A simple equivalent circuit is employed to model the optically induced switching conditions of the MIST, thereby permitting the delay time, rise time and fall time to be calculated. The model also enables easy examination of the dependence of the MIST's transient behaviour to both optical power overdrive and device capacitance and resistance. Experimental verification of the theory is undertaken.

Initialization display method of meter

Abstract: PURPOSE:To obtain a rich fashionable meter by a method wherein the display other than zero is indicated on the indicator during the rise time when power is supplied to the meter. CONSTITUTION:When power source switch S0 is closed, microcomputer 10 and the peripheral circuits rise for the normal state. Before capacitor 5 of the integrator is initialized, indicator 11 displays a symbol. When initialized, the integrator integrates the input voltage for a certain time, and thereafter, reference voltage 3 of inverse polarity is integrated until the initialized level is restored. Until this mode, indicator 11 displays zero and after this mode is over, it displays the measured values.