- Dec 06 Tue 2016 10:10
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fw: circuit-level, device-level, process-level
- Nov 28 Mon 2016 19:51
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MIT台灣誌片尾曲 - From taipei to oulan bator
- Nov 28 Mon 2016 16:58
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fw:硬體描述語言VHDL & Verilog設計導論 作者：蔡宏儒
- Nov 27 Sun 2016 15:43
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DC Biasing, Load Line Analysis, Limits of Operation
What is DC biasing? If in terms of how a device is supplied with electricity, it is a method of providing a fixed value of either voltage or current.For instance, a power supply gives a constant value of voltage or current. A parametric analyzer sweep a value, and it is used to obtain the DC transfer function. Now, nothing prevent people using an SMU to bias a circuit (i.e.use it as power supply). If instead of sweeping a voltage (or current) have the SMU set to deliver a fixed value. A SMU provides a voltage and current,it is controlled in a way that you can sweep either. So SMU can be used as a DC supply or to characterize device in DC. From diodes prospective, biasing accounts for: Externally applying a diode a DC voltage source, which is presented by a battery, there will be a pn junction potential formed internally. Thus the current is conducted only in one direction, but blocked in the opposite direction. This is how forward-biased and reverse-biased de_ned.[11] From BJTs prospective, bias-ing means externally providing each terminal with a constant voltage value by externally connecting to a DC voltage source which can be batteries or DC power supplies. Because BJT has three terminals, its DC supply voltages are normally indicated as: VEE, VBB and VCC. ..Figure 8.1: A transistor is characterized by the relationships between currents and voltages at both input and output. The Input Characteristics is the IV characteristics curves that are measured at the emitter base junction.Iin = f(Vin). The Output Characteristics is the IV characteristic curves that are measured at the base collector junction.A SMU provides a voltage and current, it is controlled in a way that you can sweep between specified values. So it can be used as a DC supply or to characterize device in DC. indicated as: VE, VB and VC, respectively. Two junctions voltages VEB and VBC are formed by its three terminals VE VB VC, respectively. For the former junction VEB, forward-biased (VEB > 0) is always needed in order to switch on the device. But for the later junction VBC, both forward-biased (VBC > 0) and reverse-biased (VBC < 0) are possible. The two biasing conditions will result in two complete di_erent operation modes. One is the saturation mode,which is used in digital electronics. The other is the active mode, used in analogue electronics. When VBC is forward-biased(VBC > 0), BJT is used as a switch in digital electronics. When VBC is reverse-biased (VBC < 0), BJT is functioning as an ampli_er in analogue electronics. [11]The established constant values at BJTs three terminals are named as: the bias point or the quiescent point (Q-point) or the DC operating point. The Q-point can be further stabilized against and temperature by replacing the Bias Schemes, such as : voltage divider bias , emitter feedback bias, current source bias...etc. The position of the DC voltage level decides if the waveform of the AC signal that fed in the input port can expand its fully swing( amplification) without being clipped the output port. To put it simply, when a BJT is biased, regardless its operation modes, all its threes terminals are provided with constant values of voltages and currents.[11] From amplifiers prospective, it does not matter what is inside the black box. What does matter is the connection outside the black box.[37] "Biasing" refers to all the external power supply networks or circuits arrangement that connected to its input and output ports to ensure the constant (V, I) levels. Figure 8.2: The _gure on the top left is the input characteristics, which plots IB versus VBE with a constant VCE. Where IB is an exponential function of VBE.The input bias point Qin(VBE, IB) is determined from the intersection between the input load line and the input characteristics. The figure on the top right is the output characteristics, which plots IC versus VCE with IB as the varing parameter. The output bias point Qout(VCE, IC) is determined. The output bias point Qout (VCE, IC) is the intersection between the output load line and the output characteristics. The two schematics below are for DC biasing BJT in CE con_guration. In the measurement of output characteristics, instead of forcing a voltage source VBB to the base, a current source IB is employed. The replacement in the bias current source at the base is to prevent the self-heating effects. 65
- Nov 25 Fri 2016 21:27
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fw: 最感動我的卡通 Slam Dunk
- Nov 15 Tue 2016 23:33
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fw: 男陰陽師角色曲
- Nov 09 Wed 2016 16:02
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fw:社民党推新移民法 目标瞄准专业人士
（德国之声中文网）莫名其妙、遮遮掩掩、"官僚怪兽"、漫无头绪：对管理外国劳工移民德国的众多法规，社民党议会党团内政发言人布尔卡德· 利施卡（Burkhard Lischka）找不出好的形容词。对既非欧盟公民，也非难民，而是到德国来工作的外国人，德国有50种不同的居留许可。利施卡评价说："即便法律系毕业，也没法闹明白。"
"一场噩梦"，哈妮·尤素福（ Hani Yousuf ）谈起和德国当局打交道的经历时这样说道。这位巴基斯坦记者生活在卡拉奇。在接受德国之声电话采访时，她越说越生气。6年前，她向德国当局递交了到德国工作半年的签证申请。德国使馆工作人员既不愿提供帮助，也不灵活机动，而且"非常不礼貌"，哈妮·尤素福这样说道。虽然她最后获得了签证，但这一切留下了不愉快的记忆。有了这次经历之后，她没什么兴趣再来德国工作了。"除非是提供特别好的条件"，哈妮·尤素福补充道，"否则我宁愿去加拿大，在那里，技术移民会受到相应的对待。"
哈妮·尤素福的情况不在少数。虽然有人也有好的经历，但总的来说，优秀的专业人才认为德国并非受欢迎的移民国家。
社民党议会党团主席托马斯·奥珀曼（Thomas Oppermann）认为，在争取专业人才的国际竞争中，德国尚需努力，因为其它国家，比如加拿大、英国和北欧国家常常更具吸引力。
低生育率意味着德国需要更多移民
然而，在今后数年以及数十年里，德国对移民却又相当的需求。德国的人口在萎缩，经济协会对缺乏专业人才发出了警告，并呼吁吸收更多移民。
借鉴加拿大模式
德国社民党早就呼吁出台移民法。现在，该党希望通过推出新的法律草案，简化移民程序。社民党在柏林提交的草案遵循加拿大模式：申请者在网上登记，按照学历、语言掌握情况、应聘职位，年龄、工作经历，是否在德国有亲属等获得相应积分，然后进入一个排名表。已经得到具体工作岗位的申请者，排名会提高。有多少申请者最后能获准前往德国，将由德国联邦议会每年决定。社民党建议从每年吸收2万5000位工作移民开始。
根据德国的需要以及排名次序，申请者将受到德国驻外使领馆和安全机构的审查，之后获知是否能来德国。他们一开始将得到三年的工作许可。"如果一切顺利"，奥珀曼说，"他们将获得无限期工作许可。"得到工作岗位的移民可以携带核心家庭成员来德，也就是伴侣和子女，前提是能够支付他们的生活费用。
难民没有积分
奥珀曼介绍说，这是一个"主要以需求为导向的制度"。同时，他也将这一制度与难民程序划开界限，也就是难民不能参加积分体系。他说，社民党不会用这样的方式刺激外国人作为难民来到德国，然后在这里提出申请，但是，如果有这么一条合法途径来德国，那么也会减轻德国避难体制的负担。
新的法律草案将简化移民程序，方便专业人士留居
贝特斯曼基金会移民问题专家奥尔坎·科瑟曼（Orkan Kösemen）等却对是否需要新的移民法表示怀疑。他在接受德国之声采访时说，现在已经有在欧盟法规的基础上管理工作移民的机制，也就是欧盟蓝卡和为找工作者提供的半年签证。"机制已经有了，只是政府没有进行充分交流。"结果就是，很少有人询问这样的可能性，有意移民的外国专业人才宁可去英语国家寻找机会。他认为，如果能够整合所有机制，让程序更为透明，那将是一个很大的进步。
社民党的法律草案是否能取得成功尚不知晓。社民党正在努力说服联合执政伙伴。奥珀曼希望在本届政府任期内通过该议案。但由于明年德国将进入联邦议院大选选战，这一愿望实现起来可能比较困难。虽然基民盟在数月的讨论后于2015年底宣布赞成推出新的移民法，但姊妹党基社盟却希望制定更为严格的移民标准，并且呼吁制定"上限法"。基社盟上周末通过的基本纲领中写道，除了工作技能、经济界的需求外，选择移民也应更多考虑到文化圈是否接近这些因素。
- Nov 05 Sat 2016 23:42
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fw:霹靂配樂 聖戟神嘆
