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1、运算放大器使用指南 的OP可能会进入阻塞状态。LM107可以避免上述问题，另外也可以选用高速OP，LM102。 10j h b c d数字签名人 j h b c d D N：c n = j h b c d , o = SW U ST , o u = In f o r m a t i o n a n d c o n t r a l c o l l e g e , c = CN 日期 ：2 0 0 4. 10 . 16 14: 17 : 53 + 0 8 0 0 签名 未验 证An Applications Guide for OP Amps 5. Summing Amplifier 加法器：加法
2、器： The summing amplifier, a special case of the inverting amplifier, is shown in Figure 4. The circuit gives an inverted output which is equal to the weighted algebraic sum of all three inputs. The gain of any input of this circuit is equal to the ratio of the appropriate input resistor to the feedb
3、ack resistor, R4. Amplifier bandwidth may be calculated as in the inverting amplifier shown in Figure 1 by assuming the input resistor to be the parallel combination of R1, R2, and R3. Application cautions are the same as for the inverting amplifier. If an uncompensated amplifier is used, compensati
4、on is calculated on the basis of this bandwidth as is discussed in the section describing the simple inverting amplifier. The advantage of this circuit is that there is no interaction between inputs and operations such as summing and weighted averaging are implemented very easily. 求和电路是反相放大器的一种特殊形式。
5、 如图图4。 其输出电压为3个输入电压加权代数和 取反（因为其为反相电路，其每路的增益为负值译者）。每路输入电压的增益等于其反 馈电阻和输入电阻之比（取反译者）。增益带宽的计算方式和反相放大电路相同，参见 例1，将其输入电阻替换为R1、R2、R3的并联电阻值。应用上的注意事项和反相放大电路相 同。如果使用了没有内部补偿功能的OP，应该在简单反相器的带宽的基础上计算补偿量。 这个电路的特点在于： 各个输入之间相互不影响， 求和或者取平均的功能很容易就可以实现。 11运算放大器使用指南 6. The Difference Amplifier 差分放大器：差分放大器： The difference
6、amplifier is the complement of the summing amplifier and allows the subtraction of two voltages or, as a special case, the cancellation of a signal common to the two inputs. This circuit is shown in Figure 5 and is useful as a computational amplifier, in making a differential to single-ended convers
7、ion or in rejecting a common mode signal. Circuit bandwidth may be calculated in the same manner as for the inverting amplifier, but input impedance is somewhat more complicated. Input impedance for the two inputs is not necessarily equal; inverting input impedance is the same as for the inverting a
8、mplifier of Figure 1 and the non-inverting input impedance is the sum of R3 and R4. Gain for either input is the ratio of R1 to R2 for the special case of a differential input single-ended output where R1 = R3 and R2 = R4. The general expression for gain is given in the figure. Compensation should b
9、e chosen on the basis of amplifier bandwidth. Care must be exercised in applying this circuit since input impedances are not equal for minimum bias current error. 12An Applications Guide for OP Amps 差分放大器是对求和电路的发展， 这种电路可以减小甚至去处两个输入信号中的共模成 分。电路见图图5，这种电路在运算电路中相当有用，比如差分对单端的转换，抑制共模信号。 电路带宽的计算方式和反相电路相同。
10、输入阻抗的计算方式相对复杂。 两个输入端的输 入阻抗没有必要相等； 反相放大部分的输入阻抗和反相放大器的计算方法相同。 同相放大部 分的输入阻抗为R3、R4之和。在R1=R3，R2=R4，差分输入，单端输出的特殊情况下，两 个输入的增益都是R2/R1。一般情况下增益的计算方法见图中说明。补偿可以按照放大器的 具体带宽进行。在应用中应该注意一点：两端的输入阻抗是不相等的，要注意输入偏置电流 的引起的误差。 13运算放大器使用指南 7. Differentiator 微分器：微分器： The differentiator is shown in Figure 6 and, as the name
11、implies, is used to perform the mathematical operation of differentiation. The form shown is not the practical form, it is a true differentiator and is extremely susceptible to high frequency noise since AC gain increases at the rate of 6 dB per octave. In addition, the feedback network of the diffe
12、rentiator, R1C1, is an RC low pass filter which contributes 90 phase shift to the loop and may cause stability problems even with an amplifier which is compensated for unity gain. A practical differentiator is shown in Figure 7. Here both the stability and noise problems are corrected by addition of
13、 two additional components, R1 and C2. R2 and C2 form a 6 dB per octave high frequency roll-off in the feedback network and R1C1 form a 6 dB per octave roll-off network in the input network for a total high frequency roll-off of 12 dB per octave to reduce the effect of high frequency input and ampli
14、fier noise. In addition R1C1 and R2C2 form lead networks in the feedback loop which, if placed below the amplifier unity gain frequency, provide 90 phase lead to compensate the 90 phase lag of R2C1 and prevent loop instability. A gain frequency plot is shown in Figure 8 for clarity. 14An Application
15、s Guide for OP Amps 15运算放大器使用指南 微分器的电路如图图6，其用于实现数学上的微分运算。这里给出的电路形式不是实际的 应用形式。由于其6dB/2倍频程的交流增益特性，其对高频噪声将相当敏感。反馈环路中， R1C1组成了一个等效的低通滤波器，由于其在反馈环中90的相移，即使对单位增益采取了 补偿措施，在这里也可能出现稳定性问题。 图图7为微分器的实际应用电路。这个电路考虑了稳定性因素和噪声因素，增加了R1和C2。R2-C2在反馈环路上构成了一个6dB/2倍频程的高频衰减网络，R1-C1在输入上构成了一个6dB/2倍频程衰减网络，这样，整个频率特性呈现为12dB/2倍频程
16、的高频衰减，抑制了由于高频信号输入OP所带来的噪声。R1C1、R2C2一同在反馈环路上构成了一个网络，如果将其频点设置在OP的单位增益带宽之内，其将提供90前向相移，以补偿由R2-C1带来的90相位滞后，提高环路的稳定性。波特图如图图8所示。 16An Applications Guide for OP Amps 8. Integrator 积分器：积分器： The integrator is shown in Figure 9 and performs the mathematical operation of integration. This circuit is essentially a low-pass filter with a frequency response decreasing at 6 dB per octave. An amplitude-frequency plot is shown in Figure 10. The circuit must be provided with an extern
