【正文】 感興趣的讀者可參考由威廉姆斯編輯的列在參考文獻中的參考文本,以及康納利和彩于1992出版的關于SPICE建模的書。 (a) 接近理想的運算放大器。 玻意耳模型不能精確模擬噪聲影響,也不能充分模擬PSRR和CMRR效應。 R1 C1 = 5HZPOLE E2 (5, 0) (4, 0) ROUT 5 6 75 .ENDS OA741 () 使用最廣泛的運算放大器宏模型,包括直流偏置效果是玻意耳模型[玻意耳以及其他人,1974年)。一個不包括非理想補償效應的更為完整的模式可以構建如分支電路文件OA741的運算放大器OA741如圖4(b)。一個完美/理想化的運算放大器的簡單的宏模型可以簡單地闡明為 SPICE分支電路文檔（表明一個沒有通過文檔處理的意見）。開爾文)時給出的。 ZIN 和R1 ZCM。因為噪音是一個隨機變量。事實是，運放的輸入階段的這兩個晶體管可能不能完美的平衡是通過相等的與輸入端串聯(lián)的輸入補償電壓源 VOS表示的。運放的開環(huán)增益不再是無限的,而是被模擬為網(wǎng)絡的輸出阻抗Zout(它可能僅僅是一個電阻,但也可能是一個系列RL網(wǎng)絡）串聯(lián)一個源A(s),其中包括了運放所有的開環(huán)極點和零點如這里的 AOL是有限的直流的開環(huán)增益,當頻率極點為wp1, wp2 , . . .且零點在 wZ1等。從此處，輸出電壓是在RF 和R1上流掉的電壓之和，或是相反，對于反相連接，源電壓vi時的輸入阻抗現(xiàn)在為無限大。兩種接近的理想最困難情況是應對大輸出電流能力和不依靠頻率的增益的要求。盡管前面提到的對理想運放的要求在實際實現(xiàn)中是不可能的，現(xiàn)在的設備能十分接近這些情況。這個共同信號指共模信號，制造商詳述這個結果是由于運放的共模抑制比（它是運放的開環(huán)增益AOL與共模增益ACM的比率）形成的；因此，對于理想運放的共模抑制比為無窮大。理想運算放大器理想運算放大器是直流耦合放大器，擁有兩個輸入端，通常只有一個輸出端（盡管少數(shù)情況下時常有不同的輸出）。當運放是一個以真正復雜的模型為特征時，信號寄生回路引起的直流接地假象將會十分復雜。目前出現(xiàn)了許多主要生產(chǎn)高質量運放的制造商。運算放大器是早期電子自動控制裝置綜合器和用于不同方程式的特定的模擬計算機的基本模塊，隨著單片整體式集成電路運算放大器(UA709，早期由鮑博?韋德拉設計，之后由飛兆半導體公司設計)在1965年出現(xiàn)。 instead the average input bias current and offset current are specified asThe output noise effects can be obtained using the model of Fig. 3 along with the circuits of aswhere it is assumed that a resistor R2 is also in series with the noninverting input of either Fig. 2(a) or (b). The thermal noise (often called Johnson or Nyquist noise) due to the resistors R1 , R2 , and RF is given by (in rms volt2/Hz)where k is Boltzmann’s constant and T is absolute temperature (176。 thus, the output voltage change due to a mon input signal will be zero. This mon signal is referred to as a monmode signal, and manufacturers specify this effect by an op amp’s monmode rejection ratio (CMRR), which relates the ratio of the openloop gain ( AOL ) of the op amp to the monmode gain (ACM ). Hence, for an ideal op amp CMRR =165。.5. A somewhat analogous specification to the CMRR is the powersupply rejection ratio (PSRR), which relates the ratio of a power supply voltage change to an equivalent input voltage change produced by the change in the power supply. Because an ideal op amp can operate with any power supply, without restriction, then for the ideal device PSRR =165。Kelvin). To obtain the total output noise, one must multiply the E2 out expression of Eq. () by the noise bandwidth of the circuit, which typically is equal to p/2 times the –3 dB signal bandwidth, for a singlepole response system [Kennedy, 1988].SPICE Computer ModelsThe use of op amps can be considerably simplified by puteraided analysis using the program SPICE. SPICE originated with the University of California, Berkeley, in 1975 [Nagel, 1975], although more recent userfriendly mercial versions are now available such as HSPICE, HPSPICE, ISSPICE, PSPICE, and ZSPICE, to mention few of those most widely used. A simple macromodel for a nearideal op amp could be simply stated with the SPICE subcircuit file (* indicates a ment that is not processed by the file).SUBCKT IDEALOA 1 2 3*A nearideal op amp: (1) is noninv, (2) is inv, and (3) is output.RIN 1 2 1E12E1 (3, 0) (1, 2) 1E8.ENDS IDEALOA ()The circuit model for IDEALOA would appear as in Fig. 4(a). A more plete model, but not including nonideal offset effects, could be constructed for the 741 op amp as the subcircuit file OA741, shown in Fig. 4(b)..SUBCKT OA741 1 2 6*A linear model for the 741 op amp: (1) is noninv, (2) is inv, and