Rise time

About: Rise time is a research topic. Over the lifetime, 4748 publications have been published within this topic receiving 47512 citations.

Analog Multiplier Based on the Hall Effect

Abstract: The Hall effect is shown to be well fitted for electronic multiplication of voltages—one of the most cumbersome operations in analog computation. The use of this effect yields a very simple instrument with good accuracy and speed. The rise time—corresponding to a 0.2% error in amplitude—for the response of a step voltage of maximum value (100 volts) applied to the slower of the two inputs, can be kept down to about 1 msec. This time is dictated only by the feeding circuits and is linearly dependent on the amplitude of the step. Thus a step of 5 volts gives a rise time of 50 μsec. Most semiconductors are investigated with respect to their capabilities of accurate multiplication. Silicon is found to be the best choice. The choice of dimension of the semiconductor crystal is discussed from the solution of a potential problem with skew boundary conditions which determines the Hall voltage. The output of a silicon crystal may be as high as about 0.5 volt for an applied magnetic induction of 5000 gauss, a current through the crystal of about 5 ma, and with a simple thermal contact between the crystal and the core of the magnet, without having errors greater than 0.1%. The output voltage is amplified with a chopper amplifier to 20 volts.

Count discriminating fire detector

Abstract: A detecting circuit is responsive to the change in a physical parameter indicative of a fire such as smoke, heat, flame or the like, and a comparator circuit connected to the detecting circuit produces detection pulses in synchronism with an oscillator circuit when the change in the physical parameter exceeds a predetermined amount. A counter circuit counts the detection pulses and produces an output which triggers a switching circuit when a predetermined number of consecutive detection pulses are counted. When triggered, the switching circuit transmits an alarm signal to an alarm receiving panel. Connected between the counter circuit and the switching circuit is a monostable multivibrator having a time constant which is equal to or smaller than the supply voltage rise time constant of the counter circuit so as to prevent the trigger signal from being applied to the switching circuit during the transition period immediately following the connection of the power source. A detection sensitivity validation means directs the detection pulses from the comparator circuit to the outside so as to facilitate the sensitivity adjustment.

Programmable semiconductor switch for a display matrix or the like and method for making same

Abstract: A semiconductor switch having symmetrical, nonlinear current-voltage characteristics has a threshold value which is programmed using a light beam after assembly of the switch. The switch preferably comprises an n+ -i-n+ device where the intrinsic material is an amorphous semiconductor alloy such as amorphous, hydrogenated or fluorinated silicon having a density and energy distribution of localized defect states in the band gap thereof forming deep traps which affect the threshold value. The highly doped n+ layers function to inject electrons into the intrinsic material and block the migration of holes. The device exhibits space charge limited current conduction and thus, increased nonlinearity under AC excitation. The switch may be employed in addressing display elements such as liquid crystal pixels in order to increase the rise time of pixel response and isolate the pixels from cross-talk, noise or other spurious signals. The n+ -i-n+ device is deposited on a glass substrate along with electrodes and address lines required for switching the pixels. Following deposition, the threshold voltage of the device is programmed by directing a light beam through a partially transparent metal contact covering the n+ -i-n+ material sandwich. The programming may be performed near the end of the fabrication process by directing the light beam through the glass plate on which the device is deposited. Following threshold programming, the device is sealed against further exposure to ambient radiation which might subsequently alter the threshold voltage.

Robust fast controller design via nonlinear fractional differential equations.

Abstract: A new method for linear system controller design is proposed whereby the closed-loop system achieves both robustness and fast response. The robustness performance considered here means the damping ratio of closed-loop system can keep its desired value under system parameter perturbation, while the fast response, represented by rise time of system output, can be improved by tuning the controller parameter. We exploit techniques from both the nonlinear systems control and the fractional order systems control to derive a novel nonlinear fractional order controller. For theoretical analysis of the closed-loop system performance, two comparison theorems are developed for a class of fractional differential equations. Moreover, the rise time of the closed-loop system can be estimated, which facilitates our controller design to satisfy the fast response performance and maintain the robustness. Finally, numerical examples are given to illustrate the effectiveness of our methods.

Transient performance of SiC MOSFETs as a function of temperature

Abstract: This research was completed to study the effects of extreme transient conditions on Silicon Carbide MOSFET devices. Two different transient conditions that are common in power converters were studied in this paper. The first is effects of voltage rise time, or dV/dt, on these devices. The second is the effects of current pulses with short pulse width and high peak currents. Both of these tests were conducted at temperatures of 150 °C to determine the performance of these devices in high stress environments. For both of these experiments, testing apparatus had to be designed and built to create these specific conditions.