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1.
The pulsed microwave damage trend of a bipolar transistor as a function of pulse parameters 下载免费PDF全文
In the present paper we conduct a theoretical study of the thermal accumulation effect of a typical bipolar transistor caused by high power pulsed microwaves(HPMs),and investigate the thermal accumulation effect as a function of pulse repetition frequency(PRF) and duty cycle.A study of the damage mechanism of the device is carried out from the variation analysis of the distribution of the electric field and the current density.The result shows that the accumulation temperature increases with PRF increasing and the threshold for the transistor is about 2 kHz.The response of the peak temperature induced by the injected single pulses indicates that the falling time is much longer than the rising time.Adopting the fitting method,the relationship between the peak temperature and the time during the rising edge and that between the peak temperature and the time during the falling edge are obtained.Moreover,the accumulation temperature decreases with duty cycle increasing for a certain mean power. 相似文献
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提出了一个描述半导体光放大器(SLA)对皮秒脉冲的放大这一物理过程的较为完善的物理模型,并数值分析了光脉冲经SLA放大后的上升时间和下降时间.结果表明:随着SLA偏置电流的增大,上升时间将缩短而下降时间将延长;输入脉冲的大峰值功率将加速上升时间的缩短和下降时间的延长;增益压缩对脉宽为几个皮秒的输入脉冲的上升时间和下降时间有明显的影响,而对脉宽为几十皮秒的输入脉冲可近似认为没有影响;增益非对称和漂移强烈影响上升和下降时间.
关键词:
半导体光放大器
皮秒光脉冲
上升和下降时间 相似文献
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本文主要简介我国变象管、双近贴象增强器毫微秒分幅相机的研制现状,并讨论这些相机的快门脉冲发生器电路。同时还介绍了用于带微通道板光电倍增管的选通电路。这些电路作适当修改后可用于微光硅靶摄象管的控制,高压电器特性试验,毫微秒脉冲源以及激光调制等场合中。 相似文献
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Designing power heterojunction bipolar transistors with non-uniform emitter finger lengths to achieve high thermal stability 下载免费PDF全文
With the aid of a thermal-electrical model,a practical method for designing multi-finger power heterojunction bipolar transistors with finger lengths divided in groups is proposed.The method can effectively enhance the thermal stability of the devices without sacrificing the design time.Taking a 40-finger heterojunction bipolar transistor for example,the device with non-uniform emitter finger lengths is optimized and fabricated.Both the theoretical and the experimental results show that,for the optimum device,the peak temperature is lowered by 26.19 K and the maximum temperature difference is reduced by 56.67% when compared with the conventional heterojunction bipolar transistor with uniform emitter finger length.Furthermore,the ability to improve the uniformity of the temperature profile and to expand the thermal stable operation range is strengthened as the power level increases,which is ascribed to the improvement of the thermal resistance in the optimum device.A detailed design procedure is also summarized to provide a general guide for designing power heterojunction bipolar transistors with non-uniform finger lengths. 相似文献
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Hyperthermia effects (39-44°C) induced by pulsed high-intensity focused ultrasound (HIFU) have been regarded as a promising therapeutic tool for boosting immune responses or enhancing drug delivery into a solid tumor. However, previous studies also reported that the cell death occurs when cells are maintained at 43°C for more than 20 minutes. The aim of this study is to investigate thermal responses inside in vivo rabbit auricular veins exposed to pulsed HIFU (1.17 MHz, 5300 W/cm2 , with relatively low-duty ratios (0.2%-4.3%). The results show that: (1) with constant pulse repetition frequency (PRF) (e.g., 1 Hz), the thermal responses inside the vessel will increase with the increasing duty ratio; (2) a temperature elevation to 43°C can be identified at the duty ratio of 4.3%; (3) with constant duty ratios, the change of PRF will not significantly affect the temperature measurement in the vessel; (4) as the duty ratios lower than 4.3%, the presence of microbubbles will not significantly enhance the thermal responses in the vessel, but will facilitate HIFU-induced inertial cavitation events. 相似文献
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为得到工业需要的大电流高重频方波脉冲,分析并改进了半导体全控型Marx发生器,在充电的同时实现了截尾功能。设计采用新型半浮栅结构晶体管 (SFGT)作为主开关,可产生kV高压、百A大电流、高重频的方波脉冲。优化了电路结构,解决直流充电源受脉冲电源放电电压冲击问题。研制得到电流100 A、频率4 kHz、脉宽4 s、负高压6 kV、上升沿下降沿均在80 ns内的方波脉冲发生器。研究了相应的SFGT磁芯隔离驱动电路,结合了SFGT栅极并联自主电容隔离驱动和IR2110的半桥驱动电路,并对半桥上的MOS管的栅极等效电路进行了理论分析,驱动电路具有抗干扰能力强且脉宽调节范围大的特点。 相似文献
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Damage effect and mechanism of the GaAs high electron mobility transistor induced by high power microwave 下载免费PDF全文
In this paper, we present the damage effect and mechanism of high power microwave(HPM) on Al GaAs/GaAs pseudomorphic high-electron-mobility transistor(p HEMT) of low-noise amplifier(LNA). A detailed investigation is carried out by simulation and experiment study. A two-dimensional electro-thermal model of the typical GaAs p HEMT induced by HPM is established in this paper. The simulation result reveals that avalanche breakdown, intrinsic excitation, and thermal breakdown all contribute to damage process. Heat accumulation occurs during the positive half cycle and the cylinder under the gate near the source side is most susceptible to burn-out. Experiment is carried out by injecting high power microwave into GaAs p HEMT LNA samples. It is found that the damage to LNA is because of the burn-out at first stage p HEMT. The interiors of the damaged samples are observed by scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS). Experimental results accord well with the simulation of our model. 相似文献
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为了提高多发射极功率异质结双极晶体管的热稳定性,本文利用耦合热阻表征发射极指间距变化对发射极指间热耦合作用的影响,得到了耦合热阻与发射极指间距之间的变化关系,提出了发射极非均匀指间距技术.通过热电反馈模型对采用发射极非均匀指间距技术的功率HBT进行热稳定性分析,得到了多发射极指上的温度分布.结果表明,多发射极HBT在采用非均匀发射极指间距技术后,峰值温度明显下降,温度变化幅度更加平缓,有效地提高了器件的热稳定性.
关键词:
异质结双极晶体管
耦合热阻
指间距 相似文献
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全固态快沿脉冲源具有小型化、高稳定性、高重复频率、输出功率低等特点,为了克服单个脉冲源输出功率低的问题,利用ADS仿真软件建立了多节蛇形微带线结构的功率合成器,并用实验验证了功率合成的效果。利用两路高稳定度的脉冲子源作为功率合成的两路输入,通过该功率合成器使两路快沿双指数信号合成为一路快沿双指数信号,实现了功率的提高。实验中脉冲子源的幅度为1.1kV,前沿约为2ns,脉冲宽度为10ns;两路信号合成后,输出电压为1.6kV,前沿约为2ns,脉冲宽度为18ns。实验验证了该功率合成模块的可行性,该合成模块还可推广至多路的脉冲子源的功率合成,实现提高快沿双指数脉冲功率的目的。 相似文献
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Thermal stability improvement of a multiple finger power SiGe heterojunction bipolar transistor under different power dissipations using non-uniform finger spacing 下载免费PDF全文
A method of non-uniform finger spacing is proposed to enhance thermal stability of a multiple finger power SiGe heterojunction bipolar transistor under different power dissipations. Temperature distribution on the emitter fingers of a multi-finger SiGe heterojunction bipolar transistor is studied using a numerical electro-thermal model. The results show that the SiGe heterojunction bipolar transistor with non-uniform finger spacing has a small temperature difference between fingers compared with a traditional uniform finger spacing heterojunction bipolar transistor at the same power dissipation. What is most important is that the ability to improve temperature non-uniformity is not weakened as power dissipation increases. So the method of non-uniform finger spacing is very effective in enhancing the thermal stability and the power handing capability of power device. Experimental results verify our conclusions. 相似文献
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Channel temperature determination of multifinger AlGaN/GaN high electron mobility transistor using micro-Raman technique 下载免费PDF全文
Self-heating in multifinger AlGaN/GaN high electron mobility transistor (HEMT) is investigated by micro-Raman spectroscopy. The device temperature is probed on the die as a function of applied bias. The operating temperature of AlGaN/GaN HEMT is estimated from the calibration curve of passively heated AlGaN/GaN structure. A linear increase of junction temperature is observed when direct current dissipated power is increased. When the power dissipation is 12.75 W at a drain voltage of 15 V, a peak temperature of 69.1 ℃ is observed at the gate edge on the drain side of the central finger. The position of the highest temperature corresponds to the high-field region at the gate edge. 相似文献
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设计了液体介质快脉冲击穿试验装置和电压电流测量系统,研究了重复频率、电极形状及电极间距与介质击穿场强、击穿电压和击穿时延等击穿特性参数的关系,比较了变压器油、十二烷基苯、蓖麻油三种典型液体绝缘介质在直流及快脉冲电压作用下的绝缘性能。结果表明:短脉冲持续时间下液体绝缘材料有异常高的击穿场强;重复脉冲串作用下的击穿场强比单个脉冲下明显减小,重复频率2 kHz时击穿场强减小了约30%;电极头半径大小对击穿也有影响,半径R=5 mm时,击穿电压最高;击穿时延随击穿场强减小而变长,在其他条件相同的情况下,测得击穿时延随机波动;蓖麻油的快脉冲电压绝缘性能最好,变压器油次之。 相似文献
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Thermal resistance matrix representation of thermal effects and thermal design in multi-finger power heterojunction bipolar transistors 下载免费PDF全文
The thermal resistance matrix including self-heating thermal resistance and thermal coupling resistance is presented to describe the thermal effects of multi-finger power heterojunction bipolar transistors. The dependence of thermal resistance matrix on finger spacing is also investigated. It is shown that both self-heating thermal resistance and thermal coupling resistance are lowered by increasing the finger spacing, in which the downward dissipated heat path is widened and the heat flow from adjacent fingers is effectively suppressed. The decrease of self-heating thermal resistance and thermal coupling resistance is helpful for improving the thermal stability of power devices. Furthermore, with the aid of the thermal resistance matrix, a 10-finger power heterojunction bipolar transistor (HBT) with non-uniform finger spacing is designed for high thermal stability. The optimized structure can effectively lower the peak temperature while maintaining a uniformity of the temperature profile at various biases and thus the device effectively may operate at a higher power level. 相似文献
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脉冲激光探测的最大探测距离与发射信号功率有关,根据系统发射端瞬时功率的形式,通过计算得出了脉冲激光平均发射功率和最大瞬时功率分别与驱动电流的脉冲上升沿时间、脉冲宽度、脉冲重复周期的关系.结合传输衰减、弱信号检测和信号预处理过程中的信号功率变化,得出了最大探测距离与激励电流波形参数、光电探测器参数、信号预处理电路噪声、信... 相似文献
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Channel temperature determination of a multifinger AlGaN/GaN high electron mobility transistor using a micro-Raman technique 下载免费PDF全文
Self-heating in a multifinger AlGaN/GaN high electron mobility transistor (HEMT) is investigated by micro-Raman spectroscopy. The device temperature is probed on the die as a function of applied bias. The operating temperature of the AlGaN/GaN HEMT is estimated from the calibration curve of a passively heated AlGaN/GaN structure. A linear increase of junction temperature is observed when direct current dissipated power is increased. When the power dissipation is 12.75 W at a drain voltage of 15 V, a peak temperature of 69.1°C is observed at the gate edge on the drain side of the central finger. The position of the highest temperature corresponds to the high-field region at the gate edge. 相似文献
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Hyperthermic temperatures, with potential applications in drug/gene delivery and chemo/radio sensitization, may be generated in biological tissues by applying focused ultrasound (FUS) in pulsed mode. Here, a strategy for optimizing FUS exposures for hyperthermia applications is proposed based on theoretical simulations and in vitro experiments. Initial simulations were carried out for tissue-mimicking phantoms, and subsequent thermocouple measurements allowed for validation of the simulation results. Advanced simulations were then conducted for an ectopic, murine xenograft tumor model. The ultrasound exposure parameters investigated in this study included acoustic power (3-5 W), duty cycle (DC) (10%-50%), and pulse repetition frequency (PRF) (1-5 Hz), as well as effects of tissue perfusion. The thermocouple measurements agreed well with simulation outcomes, where differences between the two never exceeded 1.9%. Based on a desired temperature range of 39-44 °C, optimal tumor coverage (40.8% of the total tumor volume) by a single FUS exposure at 1 MHz was achieved with 4 W acoustic power, 50% DC, and 5 Hz PRF. Results of this study demonstrate the utility of a proposed strategy for optimizing pulsed-FUS induced hyperthermia. These strategies can help reduce the requirement for empirical animal experimentation, and facilitate the translation of pulsed-FUS applications to the clinic. 相似文献