电气专业英语课文翻译(3)

The significance of this result is that the terminal voltage gain, which is the usable voltage gain, is independent of the parameters of the amplifier, and depends only on the external components R1 and R2. Had A0 been assumed large but finite, the terminal gain would be reduced approximately by a factor(1-1/A0), and it can be seen that with A0 of the order of 10^6:1 this factor is very close to unity. It is also assumed in the ideal amplifier that the output resistance is zero so that zero voltage drop results, internal to the amplifier. A0 is known as the open loop gain because it is the voltage gain which would result with the feedback loop open; the results of feedback with amplifiers of finite A0 are described in other lesson.

这个结论的意义在于端电压增益（这是很有用的电压增益）与放大器的参数无关，而只取决于外部元件R1和R2.若A0真的假定为很大但有限，端口电压增益就会大致下降一个系数（1-1/A0）。可以看出，由于A0属于10^6:1数量级，因此这个系数非常接近于1.在理想放大器中，假定输出电阻为0，这样在放大器内部电压将为0.因为A0是在反馈回路开路时得出的电压增益，所以他定义为开环增益。对于A0为有限的放大器反馈结果将在其他课中讲述。

Practical comstraints limit the ration of R2/R1 to about 10^6:1 maximum. Offset problems, discussed in section

2.15, place an upper limit on R2 and R1 must be large enough compared with the signal source resistance for the latter to be ignored. In practical circuits, R1 usually ranges between 1.0k and 10.0k.

In carrying out the signal analysis it is not necessary to show the DC bias supply, but of course this must be provided.

实际条件限制了R2/R1的值最大只能约为1000:1. 2.15节中讨论的偏置问题限制了R2的上限，而R1与信号源的电阻相比要足够大，以便后者可以忽略不计。在实际电路中，R1通常在1.0-10.0k范围内。在进行信号分析时，没有必要画出直流偏置电压，但这个电压当然是必须的。

The integrator circuit produces an output voltage which is proportional to the integral of the input voltage. This is the inverse mathematical operation to that of differentiation.

The lower limit on the integration is taken as zero time, which of course is arbitrary, and the initial voltage on the capacitor, Vc(0), takes into account all the charge accumulated prior to the chosen time origin. Since the capacitor may be allowed to charge for any arbitrary time t, the upper limit on the integral is the time variable t so that Vc itself is a function of time. This is often shown by use of a ―dummy variable‖ for the time in the integrand. Denoting the dummy variable by the symbol t‘, we find that Eq.(2.5) may be written as

积分器电路产生一个与输入电压的积分成正比例的输出电压，他是微分运算的逆运算。式中积分下限为0，当然这不是强求的。电容的初始电压计及了起始时间之前的所有充电结果。由于电容允许充电到任意时刻t，因此积分上限为时间变量t，这样Vc便为时间t的函数。这一点可以从积分时间中常用哑变量表示看出来。若用符号t‘表示哑变量，可以写成

However, where there is no risk of confusion, the simpler notation of Eq.(2.5) will be used.

Figure (omitted) shows how the operational voltage amplifier may be arranged as an integrator circuit. Application of the virtual ground concept gives…and….

然而在不发生混淆的情况下，可以使用比较简单的式子。图显示了电压运算放大器怎样被组成积分电路的，由虚地概念可得出。以及与方程联立可得

Thus, the output voltage is proportional to the integral of the input voltage, the constant of proportionality being1/(-RC). This is also the gain of the integrator, and as with the differentiator, it keeps the equation dimensionally correct.

因此，输出电压与输入电压的积分成正比，比例系数为。这也就是积分器增益，对于微分器其量纲也是相同的。

A microcomputer interface converts information between two forms .Outside the microcomputer the information handled by an electronic system exists as a physical signals, but within the program , it is represented numerically . The function of any interface can be broken down into a number of operations which modify the data in some way ,so than the process of conversion between the external and internal forms is carried out in a number or steps. 微机接口实现两种信息形式的交换。在计算机之外，由电子系统所处理的信息以一种物理信号形式存在，但实际程序中 ，它是用数字表示的。任一接口的功能都可分为以某种形式进行数据变换的一些操作，所以外部和内部形式的转换是由许多步骤完成的。

This can be illustrated by means of an example such as than or Fig 1,which shows an interface between a microcomputer and a transducer producing a continuously variable analog signal. transducers often produce very small out requiring amply frication, or they may generate signals .in a form that needs to be converted again before being handled by the rest of the system .For example ,many transducers these variable resistance which must be converted to a voltage by a special circuit. This process of converting the transducer output into a voltage4 signal which can be connected to the rest of the system is called signal conditioning .In the example of Figure 18.1, the sigma conditioning section translates the range lf voltage or current signals from the transducer to one which can be converted to digital forum by an analog-to-digital converter.

用图一所示的情况为例加以说明，图中展示了微型计算机和产生连续变化信号的传感器之间的接口。但传

Analog-to-digital –digital converter (ADC) is used to convert a continuously variable signal to a corresponding digital forum which can take any one of a fixed number of possible binary values .If the output lf the transducer does not vary continuously ,no ADC is necessary. In this case the signal conditioning section must convert the incoming signal to a form which can be connected directly to the next part of the interface, the input/output section lf the microcomputer itself.

模拟数字转换器（ADC）用来将连续变化的信号变成相应的数字量，这数字量可是可能的二进制数值中的一固定值。如果传感器输出不是连续变化的，就不需要模拟数字转换。这种情况下，信号调理单元 …… 此处隐藏：5239字，全部文档内容请下载后查看。喜欢就下载吧 ……