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1、Technical English,For Information Science and Electronic Engineering,1,开场白：好的英语是“读”出来的,学习任何语言都要大量阅读。“熟读唐诗三百首，不会作诗也会吟” 。大凡读得多的人，语言表达能力都比较强。 学英语也要大量阅读。英语好的人，一般说来都读过相当数量的书。只有读得多的人才能真正学好英语。 很多人热衷于做题目，以为这是学英语的正确途径。做的试题一套又一套，英语水平却并无实质性提高。 好的英语是“读”出来的，不是做练习“做”出来的。“读”出来的英语是地道的，自然的，因为学的是“语感”。“做”出来的英语往往流于生硬，因
2、为是依赖“语法规则”硬做的。,2,开场白：好的英语是“读”出来的,我主张一口气读下去，即便有个别单词挡道，只要不影响整体内容的理解，就不必停下来查词典，因为那样会打断思路，影响阅读速度，甚至扼杀阅读兴趣。 阅读主要目的在于语言吸收上的潜移默化，在于获得语感。阅读需要“量”，没有大量语言“输入”难以学好英语。国内学习者恰恰语言输入量太少，输出量就更少，往往事倍功半。 练习要做，但要适量；重要的是阅读，大量的阅读。 节引自：黄源深，英语阅读也轻松，文汇报，2004.8.2,Unit One,Electronics: Analog and Digital,Part I,Ideal Operation
3、al Amplifiers and Practical Limitations,5,New Words,6,New Words,7,1,In order to discuss the ideal parameters of operational amplifiers, we must first define the terms, and then go on to describe what we regard as the ideal values for those terms. At first sight, the specification sheet for an operat
4、ional amplifier seems to list a large number of values, some in strange units, some interrelated, and often confusing to those unfamiliar with the subject.,对这些指标项讲述我们所认为的理想值,经常使那些对运放不熟悉的人感到迷惑,8,1,The approach to such a situation is to be methodical, and take the necessary time to read and understand
5、 each definition in the order that it is listed. Without a real appreciation of what each means, the designer is doomed to failure. The objective is to be able to design a circuit from the basis of the published data, and know that it will function as predicted when the prototype is constructed.1,按照
6、列出的次序阅读并理解每一个定义,能按公布的数据设计电路，并确认构建的样机具有预计的功能,9,1,It is all too easy with linear circuits, which appear relatively simple when compared with todays complex logic arrangements, to ignore detailed performance parameters which can drastically reduce the expected performance.2,对于线性电路，它们与现在的复杂逻辑电路结构相比看起来较为
7、简单，（因而在设计中）太容易忽视具体的性能参数了，这些（参数）可极大地削弱预期性能。,本句主要结构：It is easy to ignore ,10,2 An example,Let us take a very simple but striking example. Consider a requirement for an amplifier having a voltage gain of 10 at 50 kHz driving into a 10 kW load.3 A common low-cost, internally frequency-compensated op amp
8、 is chosen; it has the required bandwidth at a closed-loop gain of 10, and it would seem to meet the bill.4 The device is connected, and it is found to have the correct gain.,考虑对一个50kHz频率时电压增益为10的放大器驱动10kW负载时的要求 （注意at和into的用法）,看来满足价格要求 （bill：帐单）,11,2,But it will only produce a few volts output swing
9、 when the data clearly shows that the output should be capable of driving to within two or three volts of the supply rails.5 The designer has forgotten that the maximum output voltage swing is severely limited by frequency, and that the maximum low-frequency output swing becomes limited at about 10
10、kHz.,它只能产生几伏的电压输出范围，然而数据却清楚地显示输出应能驱动达到电源电压范围以内2到3伏。,12,2,Of course, the information is in fact on the data sheet, but its relevance has not been appreciated. This sort of problem occurs regularly for the inexperienced designer. So the moral is clear: always take the necessary time to write down the
11、full operating requirements before attempting a design. Attention to the detail of the performance specification will always be beneficial. It is suggested the following list of performance details be considered:,注意句型：It is suggested the list be considered.,13,2,Closed loop gain accuracy, stability
12、with temperature, time and supply voltage Power supply requirements, source and load impedances, power dissipation Input error voltages and bias currents. Input and output resistance, drift with time and temperature Frequency response, phase shift, output swing, transient response, slew rate, freque
13、ncy stability, capacitive load driving, overload recovery,14,3,Linearity, distortion and noise Input, output or supply protection required. Input voltage range, common-mode rejection External offset trimming requirement Not all of these terms will be relevant, but it is useful to remember that it is
14、 better to consider them initially rather than to be forced into retrospective modifications.,而不要被迫返工,15,4 All parameters are subject to wide variations,Never forget this fact. How many times has a circuit been designed using typical values, only to find that the circuit does not work because the de
15、vice used is not typical?6 The above statement thus poses a tricky question: when should typical values and when should worst-case values be used in the design?,有多少次是在用典型值设计好电路后发现（该电路）只是因为使用的器件不典型而不能工作？,在设计中何时应该使用典型值，何时应该使用最不利值？,16,4,This is where the judgment of the experienced designer must be bro
16、ught to bear. Clearly, if certain performance requirements are mandatory, then worst-case values must be used. In many cases, however, the desirability of a certain defined performance will be a compromise between ease of implementation, degree of importance, and economic considerations.7,某一规定的性能是否可取要在易实现性，重要性，经济性之间取得折中。,17,5 Do not over-specify or over-design,In the end, we are all controlled by cost, and it is really pointless taking a sledgehammer to crack a nut, Simplicity is of the
