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1、Unit 4 Operational Amplifier,运算放大器,Part One Electronics,Preparing for the text:,Technical terms: 1. operational amplifier 运算放大器 2. inverting input 反向输入端 3. non-inverting input 同向输入端 4. 8 pin dual-in line 8管脚双列直插式 Questions for text discussion: Why is operational amplifier given the name? Because it
2、was originally applied to high gain amplifiers which can perform certain mathematical operations. 2. Draw the circuit symbol of an operational amplifier. 3. Talk about the applications of the operational amplifiers. It has a wide range of applications in such fields as analogue signal operations, am
3、plification, fitering, waveforms producing，linear and non-linear signals handling, etc.,The main idea of this unit:,This unit mainly discusses the basic knowledge about operational amplifier.,1. Operational amplifier can perform certain mathematical operations.,2.These high gain amplifiers are now u
4、sed for a wide variety of applications,applications : analogue signal operations, amplification, fitering, waveforms producing，linear and non-linear signals handling,1.amplifier mplifai n.放大器，扩音器 The amplifier can amplify the small signal. 2. analogue nl n.模拟 adj.模拟的 analogue signal analogue , digit
5、al 3. variety vraiti n.变化, 多样性, 种类 a variety of 4. discrete diskri:t adj.不连续的, 离散的 continuous , discrete 5. internal int:nl adj.内在的, 国内的 internal ,external 6. denote dinut vt.指示, 表示,New words:,7. invert inv:t vt.使颠倒, 使转化 Heat energy can be inverted light energy. 8. available veilbl adj.可获得的 9. packa
6、ge pki n.包裹, 包, 管壳 IC package 10. pin pin n.钉, 管脚，引线 8 pin dual in line 11. impedance impi:dns n.电阻抗，阻抗 The impedance of FET is very large.,a variety of 各种各样的 even though 即使 be interested in 对.感兴趣 be known as 被称为 with respect to 关于, 至于 be equal to 等于，与相等,Expressions:,Learn the text:,The first paragr
7、aph: The operational amplifier is the most important basic block of all linear circuits. It has a wide range applications in such fields as analogue signal operations, amplification, filtering, waveforms producing, linear and non-linear signals handing, etc. 译：运算放大器是所有线性电路中最重要的基本器件。它的应用十分广泛，包括模拟信号的运
8、算，放大，滤波，波形发生器，以及进行线性和非线性信号的处理等。,The second paragraph:,The term “operational amplifier” was originally applied to high gain amplifiers operating down to zero frequency which were used in analogue computers to perform certain mathematical operations. These high gain amplifier are now used for a wide v
9、ariety of applications, but the name “operational amplifiers” or “op-amp” is normally use even though no mathematical operation are involved. The early operational amplifier employed discrete components, but it is now much more convenient to employ an integrated circuit. The circuit designers is not
10、 generally interested in the internal components of an integrated circuit, but only in the performance of the unit as a whole. Therefore, the symbol in Fig. 2 is used to denote the amplifier. It can be seen that there are two inputs, one output and connection the positive and negative supply lines.,
11、译：运算放大器这一术语最早适用于下限频率可低到零赫兹的高增益放大器，它可用于模拟计算机中执行某些数学运算。这种高增益的放大器现在已被广泛应用于各个方面，早已远远超出数值运算的范围，但通常仍称之为运算放大器或OP-AMP。早期的运算放大器适用分立元件，但现在适用集成电路就更为方便了。电路设计者通常对集成电路内波元件并不感兴趣，只关心作为一个整体的单元性能。因此，图2所示的符号用来表示运算放大器。由图可见，运放有两个输入端，一个输出端以及正、负电源端子。,注：这里 which were used mathematical operational 为定语从句，修饰前面的 high gain ampl
12、ifiers, 因为定语从句并未直接跟在所修饰的先行次后，语法上称其为分割定语。而定语从句中的 to perform certain mathematical operations 为动词不定式短语，作目的状语。,The third paragraph:,If the inverting input is made slightly more positive, the output will become more negative, this is why the name “inverting” is given to this input. if, the non-inverting
13、input is made more positive, the output will also become more positive. 译：如果反向输入端正电压略微增加一点，那么输出负电压变得更强，这就是为什么称这个输入端为“反向输入端” 的原因。然而，如果同相收入电压正向增大，输出端正电压也将变得更强。,The fourth paragraph:,Type 741 device is one of the best known general purpose operational amplifier and is also one of the cheapest of all li
14、near integrated circuits. The device is actually available in a number of different packages. Readers will usually find the type of 741 shown in Fig. 3.This type of package is known as the 8 pin dual-in-line. 译：741型器件是众所周知的通用运算放大器之一，也是所有的线性集成电路中最便宜的一种。这种器件实际上具有不同的封装形式。读者通常会发现如图3所示的741型器件最便于使用，这种封装形式
15、为8管脚双列直插式,The fifth paragraph:,A basic circuit of a 741 inverting amplifier is shown in Fig. 4. The input signal is fed to the inverting input of 741 via R1 and therefore the output is inverted in phase respect to the input. Operational amplifier are designed to have a very high input impedance. The
16、 input currents of the 741 circuit are therefore very small. As the inverting input is virtually at ground potential, the current which flows through R1 is equal to the input voltage Ui divided by R1. Similarly, the current flowing through R3 is Uo/R3. where Uo is the output voltage. These two current are almost equal, thus the voltage gain of circuit is equa
