Topic
Rise time
About: Rise time is a research topic. Over the lifetime, 4748 publications have been published within this topic receiving 47512 citations.
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TL;DR: In this article, a 16-channel charge-sensitive preamplifier (CSA) prototype with automatic detector leakage compensation is presented, which is used to read out charge signals from a 4 times4 APD array having 3 pF of capacitance and 75 nA of leakage current per pixel.
Abstract: Design, implementation, analysis and measured performance results of a new high-speed low-noise 16-channel charge-sensitive preamplifier (CSA) prototype with automatic detector leakage compensation are presented. The prototype has been fabricated in TSMC 0.35-mum CMOS process and is designed for use with avalanche photodiode (APD) based PET detectors. The CSA is used to read out charge signals from a 4times4 APD array having 3 pF of capacitance and 75 nA of leakage current per pixel. A single channel CSA has 16 gain settings measured to range from 31.7 mV/fC to 4.5 mV/fC. The gain settings for all channels are set by a 64-bit on-chip shift register. The signal rise time at the CSA output was measured to be as fast as 2.9 ns (5%-55% rise time) and 4.8 ns (20%-80% rise time). A feedback MOS transistor biased in the triode region is used to reset the CSA output and a very slow Gm-feedback loop performs automatic leakage compensation up to 10 muA of leakage current per channel. Minimum input referred rms noise of 350 e- was measured with a pure capacitive input load and 1200 e- with an actual APD load biased at -1.7 kV connected to the CSA input, both at 0.1-mus peaking time. The prototype chip draws less than 50 mA of total current from a +3.3 V supply.
30 citations
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TL;DR: It can be concluded that the implementation complexity of both control strategies are almost identical, although the IFO control method has a much better performance than the SC control method.
Abstract: Two methods of induction motor control are examined. The indirect field-oriented (IFO) and the slip-control (SC) methods are formally compared. Their block diagrams are derived, analyzed and their similarities shown. It is demonstrated that the difference between the two is just due to a feedforward block that computes the current phase to be supplied to the motor in an IFO controller. This proves that the implementation complexity of either controller is almost identical. To perform comparative tests, both control methods were implemented using a single hardware. The torque rise time and frequency response of the speed control are presented. Based on experimental results, it is shown that the speed sensor resolution and the sampling rate of the controller strongly influence the dynamic response in the IFO method. The SC method is less sensitive to these parameters although it always presented a worse dynamic response. The IFO speed control presented a flat frequency response whereas the SC method presented a peak which could lead to an oscillatory speed response. It is also shown that the variation of the rotor electrical time constant influences strongly and in a similar way both control methods. Finally, it can be concluded that the implementation complexity of both control strategies are almost identical, although the IFO control method has a much better performance than the SC control method. >
30 citations
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TL;DR: In this paper, the response time of a GaAs/Alx Ga1−x As multiquantum well infrared detector (at a wavelength of λ=6.4 μm) was determined to be less than 300 ps.
Abstract: We have measured the response time of a GaAs/Alx Ga1−x As multiquantum well infrared detector (at a wavelength of λ=6.4 μm). The intrinsic rise time is determined to be less than 300 ps.
30 citations
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TL;DR: Pulser is capable to produce up to 1MHz pulse trains with positive 50V-1kV pulses with up to 10A peak output current and fully satisfies desired 1MHz bandwidth.
30 citations
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TL;DR: In this article, a liquid-crystal fiber Fabry-Perot tunable filter (LC-FFP-TF) with fast tuning (<33 /spl mu/s) over a 0.4-12 nm wavelength range centered at 1550 nm was presented.
Abstract: We report a liquid-crystal fiber Fabry-Perot tunable filter (LC-FFP-TF) with fast tuning (<33 /spl mu/s) over a 0.4-12 nm wavelength range centered at 1550 nm, at a temperature of 35/spl deg/C, using a commercially available electroclinic LC material, BDH764E. Typically, the fall time of the LC-FFP-TF is over an order of magnitude shorter than the rise time. For the first time to our knowledge, switching between two discrete wavelengths was demonstrated using an LC-FFP-TF.
30 citations