电子信息工程专业英语课文翻译(第3版)

电子信息工程专业英语教程第三版译者：唐亦林p32In 1945 H. W. Bode presented a system for analyzing the stability of feedback systems by using graphical methods. Until this time, feedback analysis was done by multiplication and division, so calculation of transfer functions was a time consuming and laborious task. Remember, engineers did not have calculators or computers until the '70s. Bode presented a log technique that transformed the intensely mathematical process of calculating a feedback system's stability into graphical analysis that was simple and perceptive. Feedback system design was still complicated, but it no longer was an art dominated by a few electrical engineers kept in a small dark room. Any electrical engineer could use Bode's methods find the stability of a feedback circuit, so the application of feedback to machines began to grow. There really wasn't much call for electronic feedback design until computers and transducers become of age.1945年HW伯德提出了一套系统方法，用图形化方法来分析反馈系统的稳定性。

在此之前，反馈分析是通过乘法和除法完成的，所以传递函数的计算是一项费时和费力的任务。

请记得工程师们在上个世纪70年代之前是没有计算机或者计算器的。

伯德提出了一种日志技术，这种技术将计算反馈系统稳定性这种复杂的数学过程转换为简单和直观的图像分析。

反馈系统的设计虽然还是很复杂，但它不再是几个电气工程师待在一个小黑屋里的艺术了。

任何电气工程师都可以使用伯德的方法找到一个反馈电路的稳定点，因此反馈电路在机器中的应用开始增加。

直到计算机和传感器的时代到来之前，反馈电路的设计真的没有太多的要求。

p36An integrator(Figure 5.1a) is the simplest filter mathematically, and it forms the building block for most modern integrated filters. Consider what we know intuitively about an integrator. If you apply a DC signal at the input (i.e. , zero frequency), the output will describe a linear ramp that grows in amplitude until limited by the power supplies. Ignoring that limitation, the response of an integrator at zero frequency is infinite, which means that it has a pole at zero frequency.(A pole exists at any frequency for which the transfer function’s value becomes infinite.)从数学公式上讲，积分器（见图2.1a）是最简单的滤波器；它是构成大多数现代集成滤波器的基本模块。

我们怎么从直观上理解积分器呢？假设在输入端加上一个直流信号（频率为0），那么在输出端将会出现一个线性斜坡信号,其幅度一直增至电源电压。

如果不考虑电源电压对输出信号的限制，积分器在零频率上的响应将是无穷大，这意味着它在零频率点上存在一个极点（在任何使传递函数为无穷大值的频率点上都存在一个极点）。

p38While the complex frequency’s imaginary part (jw) helps describea response to AC signals, the real part (q) helps describe a circuit’s transient response. Looking at Figure 5.2b, we can therefore say something about the RC low-pass filter’s response. Looking at Figure 5.2b, we can therefore say something about the RC low-pass filter’s response as compared to that of the integrator. The low-pass filter’s transient response is more stable, because its pole is in the negative-real half of the complex plane. That is, the low-pass filter makes a decaying-exponential response to a step-function input; the integrator makes an infinite response. For the low-pass filter, pole positions further down the - axis mean a higher 0, a shorter time constant, and therefore a quicker transient response. Conversely, a pole closer to the j axis causes a longer transient response.复频率的虚部有助于描述电路对交流信号的响应，而其实部有助于描述电路的瞬态响应。

从图2.2b中可以看出，RC低通滤波器的响应和积分器之间的一些区别。

低通滤波器的瞬态响应更加稳定，因为其极点位于复平面的左半部。

即对于阶跃函数输入，滤波器的响应是衰减指数形式的；积分器的响应是无穷大的。

对于低通滤波器而言，极点沿坐标轴离原点越远，意味着0越大，时间常数越短，瞬态响应越快。

相反的情况是：极点离j坐标轴越近，瞬态响应越慢。

p47The converter is essentially a highly over-sampling 1-bit ADC (the comparator) followed by digital filtering and decimation to realize the processing gain. The effective performance of the converter is greatlyenhanced by the addition of circuitry to shape the quantization noise such that, instead of being uniformly spread throughout the 0 to fs/2 band, it is minimized in the band of interest (Figure 6.5).这个转换器实质上是一个后跟数字滤波和抽取、高过采样率的1位模数转换器（即比较器），用来实现处理增益。

通过另外增加一个噪声整形电路去整型量化噪声，该转换器的有效性能获得了极大的提高。

噪声整形电路将原来在0~1/2sf频带内均匀分布的噪声最大限度地从有用频带中去除（见图6.5）。

p62The buck converter is capable of kilowatts of output power, but suffers from one serious shortcoming which would occur if the power switch were to fail short-circuited, the input power source is connected directly to the load circuitry with usually produces catastrophic results. To avoid this situation, a crowbar is placed across the output. A crowbar is a latching SCR which is fired when the output is sensed as entering an overvoltage condition. The buck converter should only be used for board-level regulation.降压变压器可以产生上千瓦的输出功率，但它有个致命的缺陷，当开关电源发生短路时，输入电源会直接连接到负载电路上，这会导致可怕的后果。

为了避免这种情况，要在输出端加上一个断路器。

这个电路是一个闭合的可控硅整流器，当输出端被检测到一个过高的电压时，它就被触发工作了。

降压型变换器只适合于板级调节。

p70Clock Driver Skew (Intrinsic Skew) is the amount of skew caused by the clock driver itself. There are two kinds of clock driver devices; buffer devices and PLL-based devices. Skew occurs on the output of the buffer devices because of the differences in propagation delay of the input signal through the device. A majority of this difference is attributed to differences in output loading. Skew in PLL-based devices can be very small, since a PLL-based device can be adjusted to compensate for differences in output loading.时钟驱动器偏移（固有偏移）是由时钟驱动器自己引起的偏移。