模擬電子技術(shù)基礎(chǔ)課件-9

負(fù)反饋放大電路的分析計(jì)算常用方法a.等效電路法5.3負(fù)反饋放大電路的分析及近似計(jì)算等效電路法分離法近似計(jì)算法把放大器中的非線性器件用線性電路等效，然后根據(jù)電路理論求解各項(xiàng)指標(biāo)。負(fù)反饋放大電路的分析計(jì)算常用方法a.等效電路法5.3(b)分別求出基本放大電路的A、Ri、Ro、fH和fL等指標(biāo)及反饋網(wǎng)絡(luò)的反饋系數(shù)F。(c)分別求出Af、Rid、Rof、fHf和fLf等指標(biāo)。(a)分負(fù)反饋放大電路為基本放大電路和反饋網(wǎng)絡(luò)兩部分。分離法的基本思想b.分離法(b)分別求出基本放大電路的A、Ri、Ro、fH和f由于集成運(yùn)算放大器和多級(jí)放大電路的放大倍數(shù)一般都比較大，很容易使放大電路滿足深度負(fù)反饋的條件。放大電路滿足深度負(fù)反饋的條件5.3.1深度負(fù)反饋放大電路近似計(jì)算的一般方法1.采用近似計(jì)算的條件由于集成運(yùn)算放大器和多級(jí)放大電路的放大倍數(shù)一般都比較大，很容在深度負(fù)反饋（AF>>1）的條件下··XoXi·XoXf≈·F·≈1Af=A1+AF·······F=XfXo代入上式得將XoXi··Af=·3.近似計(jì)算的原理在深度負(fù)反饋（AF>>1）的條件下··XoXi·XoXf≈·Xid≈0··XoXi·XoXf≈·由得(1)當(dāng)電路引入串聯(lián)負(fù)反饋時(shí)·Uf·Ui≈·Uid≈0(稱為虛短)·Xf·Xi≈·Xid≈0··XoXi·XoXf≈·由得(1)當(dāng)電(2)當(dāng)電路引入并聯(lián)負(fù)反饋時(shí)·If·Ii≈·Iid≈0(稱為虛斷）由于基本放大電路的電壓放大倍數(shù)也很大，條件·Uid≈0也同時(shí)成立。(2)當(dāng)電路引入并聯(lián)負(fù)反饋時(shí)·If·Ii≈·Iid≈0(1．電壓串聯(lián)負(fù)反饋（同相輸入比例放大器）5.3.2電壓模運(yùn)放組成的反饋電路+A+Uid+F++UfUiUoRLR2R1????_____1．電壓串聯(lián)負(fù)反饋（同相輸入比例放大器）5.3.2電壓根據(jù)電路在深度負(fù)反饋條件下的分析依據(jù)有Uid≈0(虛短)·U+≈U–··+A+Uid+F++UfUiUoRLR2R1????_____根據(jù)電路在深度負(fù)反饋條件下的分析依據(jù)有Uid≈0由于U+≈Ui·····+A+Uid+F++UfUiUoRLR2R1????_____由于U+≈Ui·····+A+Uid+F++UfUiUoR故電路的閉環(huán)電壓放大倍數(shù)·····+A+Uid+F++UfUiUoRLR2R1????_____故電路的閉環(huán)電壓放大倍數(shù)·····+A+Uid+F++URif≈∞閉環(huán)輸入電阻

Rof≈0閉環(huán)輸出電阻RifRof+A+Uid+F++UfUiUoRLR2R1????_____Rif≈∞閉環(huán)輸入電阻Rof≈0閉環(huán)輸出電阻RifRo2．電壓并聯(lián)負(fù)反饋（反相輸入比例放大器）

在深度負(fù)反饋條件下RL?+A+UoUsF+R1R2IiIidIf????___2．電壓并聯(lián)負(fù)反饋（反相輸入比例放大器）在深度負(fù)反饋條件下由Iid≈0(虛斷)知·Ii≈If??RL?+A+UoUsF+R1R2IiIidIf????___由Iid≈0(虛斷)知·Ii≈If??RL?+A+Uo由Uid≈0(虛短)知···RL?+A+UoUsF+R1R2IiIidIf????___由Uid≈0(虛短)知···RL?+A+UoUsF+R1R········而RL?+A+UoUsF+R1R2IiIidIf????___········而RL?+A+UoUsF+R1R2IiIid故閉環(huán)互阻增益···RL?+A+UoUsF+R1R2IiIidIf????___故閉環(huán)互阻增益···RL?+A+UoUsF+R1R2IiI閉環(huán)電壓放大倍數(shù)···RL?+A+UoUsF+R1R2IiIidIf????___閉環(huán)電壓放大倍數(shù)···RL?+A+UoUsF+R1R2IiI輸入電阻RifRL?+A+UoUsF+R1R2IiIidIf????___輸入電阻RifRL?+A+UoUsF+R1R2IiIidIf輸出電阻RofRL?+A+UoUsF+R1R2IiIidIf????___輸出電阻RofRL?+A+UoUsF+R1R2IiIidIf3．電流串聯(lián)負(fù)反饋——電壓電流變換器由于····+A+Uid+++UfUiUoRLR????Io?F_____3．電流串聯(lián)負(fù)反饋——電壓電流變換器由于····+A+U故電路的閉環(huán)互導(dǎo)增益·······+A+Uid+++UfUiUoRLR????Io?F_____故電路的閉環(huán)互導(dǎo)增益·······+A+Uid+++UfUi閉環(huán)電壓放大倍數(shù)······+A+Uid+++UfUiUoRLR????Io?F_____閉環(huán)電壓放大倍數(shù)······+A+Uid+++UfUiUoR輸入、輸出電阻RifRof+A+Uid+++UfUiUoRLR????Io?F_____輸入、輸出電阻RifRof+A+Uid+++UfUiUoRL4．電流并聯(lián)負(fù)反饋——電流放大器在深度負(fù)反饋的條件下Ii≈If··Ui≈0·+A+UoUi+F+R1R2R3???????____RL4．電流并聯(lián)負(fù)反饋——電流放大器在深度負(fù)反饋的條件下Ii輸入電流··反饋電流··+A+UoUi+F+R1R2R3???????____RL輸入電流··反饋電流··+A+UoUi+F+R1R2R3??閉環(huán)電流放大倍數(shù)·······+A+UoUi+F+R1R2R3???????____RL閉環(huán)電流放大倍數(shù)·······+A+UoUi+F+R1R2R閉環(huán)電壓放大倍數(shù)······+A+UoUi+F+R1R2R3???????____RL閉環(huán)電壓放大倍數(shù)······+A+UoUi+F+R1R2R3輸入、輸出電阻RifRof+A+UoUi+F+R1R2R3???????____RL輸入、輸出電阻RifRof+A+UoUi+F+R1R2R3?1．電壓串聯(lián)負(fù)反饋5.3.3分立元件組成的反饋電路F++–+VCCT1++T2+++–+––+1．電壓串聯(lián)負(fù)反饋5.3.3分立元件組成的反饋電路F+⊕⊕⊕(1)負(fù)反饋的判斷F++–+VCCT1++T2+++–+––+⊕⊕⊕(1)負(fù)反饋的判斷F++–+VCCT1++T2+++(2)閉環(huán)電壓放大倍數(shù)··由于F++–+VCCT1++T2+++–+––+(2)閉環(huán)電壓放大倍數(shù)··由于F++–+VCCT1++T·····F++–+VCCT1++T2+++–+––+·····F++–+VCCT1++T2+++–+––+(3)輸入電阻RifF++–+VCCT1++T2+++–+––+(3)輸入電阻RifF++–+VCCT1++T2+++–(4)輸出電阻RofF++–+VCCT1++T2+++–+––+(4)輸出電阻RofF++–+VCCT1++T2+++–2．電流并聯(lián)負(fù)反饋++VCCT1+T2+F–+++––2．電流并聯(lián)負(fù)反饋++VCCT1+T2+F–+++––⊕(1)負(fù)反饋的判斷++VCCT1+T2+F–+++––⊕(1)負(fù)反饋的判斷++VCCT1+T2+F–+++––由于反饋電流iF來(lái)自于輸出級(jí)晶體管T2集電極電流iC2故電路穩(wěn)定的是iC2，而不是負(fù)載電流iOiC2iE2iO++VCCT1+T2+F–+++––由于反饋電流iF來(lái)自于輸出級(jí)晶體管T2集電極電流iC2故(2)閉環(huán)電流放大倍數(shù)·····FiC2iE2iO++VCCT1+T2+–+++––(2)閉環(huán)電流放大倍數(shù)·····FiC2iE2iO++V(3)閉環(huán)電壓放大倍數(shù)······iC2iE2iO++VCCT1+T2+F–+++––(3)閉環(huán)電壓放大倍數(shù)······iC2iE2iO++V(4)輸入電阻RifR'ifiC2iE2iO++VCCT1+T2+F–+++––(4)輸入電阻RifR'ifiC2iE2iO++VCC(5)輸出電阻從T2集電極看進(jìn)去的閉環(huán)輸出電阻從負(fù)載看進(jìn)去的輸出電阻RofR'ofiC2iE2iO++VCCT1+T2+F–+++––(5)輸出電阻從T2集電極看進(jìn)去的閉環(huán)輸出電阻從負(fù)載看5.3.4電流模運(yùn)放的閉環(huán)特性電流模運(yùn)放同相輸入放大電路Ui?+1RiIi?RZCZ+1Ii?Uo?R1R2I2?Uf?+–5.3.4電流模運(yùn)放的閉環(huán)特性電流模運(yùn)放同相輸入放大低頻閉環(huán)電壓放大倍數(shù)在深度負(fù)反饋的條件下Ui?+1RiIi?RZCZ+1Ii?Uo?R1R2I2?Uf?+–低頻閉環(huán)電壓放大倍數(shù)在深度負(fù)反饋的條件下Ui?+1RiIi?分析電路的高頻特性Ui?+1RiIi?RZCZ+1Ii?Uo?R1R2I2?Uf?+–分析電路的高頻特性Ui?+1RiIi?RZCZ+1Ii?Uo由圖可知·······Ui?+1RiIi?RZCZ+1Ii?Uo?R1R2I2?Uf?+–由圖可知·······Ui?+1RiIi?RZCZ+1Ii?······Ui?+1RiIi?RZCZ+1Ii?Uo?R1R2I2?Uf?+–······Ui?+1RiIi?RZCZ+1Ii?Uo?R1由以上各式得電路的高頻閉環(huán)特性···由于···當(dāng)Auf0Ri<<R2時(shí)·由以上各式得電路的高頻閉環(huán)特性···由于···當(dāng)Auf0R·由式得電路的閉環(huán)上限截止頻率為結(jié)論(1)fHf僅與CZ、R2有關(guān)，而與R1無(wú)關(guān)。(2)電流模運(yùn)放的閉環(huán)電壓放大倍數(shù)增大時(shí)，帶寬增益積有所增加?！び墒降秒娐返拈]環(huán)上限截止頻率為結(jié)論(1)fHf僅與C電流模運(yùn)放幅頻特性.dB/||lg20fuAlg20R1R2R1+OfHfflg20R2+電流模運(yùn)放幅頻特性.dB/||lg20fuAlg20R1R2電壓模運(yùn)放幅頻特性電壓模運(yùn)放帶寬增益積等于常數(shù).dB/||lg20fuAlg20R1R2R1+0fHfflg20R2+電壓模運(yùn)放幅頻特性電壓模運(yùn)放帶寬增益積等于常數(shù).dB/||l負(fù)反饋放大電路的分析計(jì)算常用方法a.等效電路法5.3負(fù)反饋放大電路的分析及近似計(jì)算等效電路法分離法近似計(jì)算法把放大器中的非線性器件用線性電路等效，然后根據(jù)電路理論求解各項(xiàng)指標(biāo)。負(fù)反饋放大電路的分析計(jì)算常用方法a.等效電路法5.3(b)分別求出基本放大電路的A、Ri、Ro、fH和fL等指標(biāo)及反饋網(wǎng)絡(luò)的反饋系數(shù)F。(c)分別求出Af、Rid、Rof、fHf和fLf等指標(biāo)。(a)分負(fù)反饋放大電路為基本放大電路和反饋網(wǎng)絡(luò)兩部分。分離法的基本思想b.分離法(b)分別求出基本放大電路的A、Ri、Ro、fH和f由于集成運(yùn)算放大器和多級(jí)放大電路的放大倍數(shù)一般都比較大，很容易使放大電路滿足深度負(fù)反饋的條件。放大電路滿足深度負(fù)反饋的條件5.3.1深度負(fù)反饋放大電路近似計(jì)算的一般方法1.采用近似計(jì)算的條件由于集成運(yùn)算放大器和多級(jí)放大電路的放大倍數(shù)一般都比較大，很容在深度負(fù)反饋（AF>>1）的條件下··XoXi·XoXf≈·F·≈1Af=A1+AF·······F=XfXo代入上式得將XoXi··Af=·3.近似計(jì)算的原理在深度負(fù)反饋（AF>>1）的條件下··XoXi·XoXf≈·Xid≈0··XoXi·XoXf≈·由得(1)當(dāng)電路引入串聯(lián)負(fù)反饋時(shí)·Uf·Ui≈·Uid≈0(稱為虛短)·Xf·Xi≈·Xid≈0··XoXi·XoXf≈·由得(1)當(dāng)電(2)當(dāng)電路引入并聯(lián)負(fù)反饋時(shí)·If·Ii≈·Iid≈0(稱為虛斷）由于基本放大電路的電壓放大倍數(shù)也很大，條件·Uid≈0也同時(shí)成立。(2)當(dāng)電路引入并聯(lián)負(fù)反饋時(shí)·If·Ii≈·Iid≈0(1．電壓串聯(lián)負(fù)反饋（同相輸入比例放大器）5.3.2電壓模運(yùn)放組成的反饋電路+A+Uid+F++UfUiUoRLR2R1????_____1．電壓串聯(lián)負(fù)反饋（同相輸入比例放大器）5.3.2電壓根據(jù)電路在深度負(fù)反饋條件下的分析依據(jù)有Uid≈0(虛短)·U+≈U–··+A+Uid+F++UfUiUoRLR2R1????_____根據(jù)電路在深度負(fù)反饋條件下的分析依據(jù)有Uid≈0由于U+≈Ui·····+A+Uid+F++UfUiUoRLR2R1????_____由于U+≈Ui·····+A+Uid+F++UfUiUoR故電路的閉環(huán)電壓放大倍數(shù)·····+A+Uid+F++UfUiUoRLR2R1????_____故電路的閉環(huán)電壓放大倍數(shù)·····+A+Uid+F++URif≈∞閉環(huán)輸入電阻

Rof≈0閉環(huán)輸出電阻RifRof+A+Uid+F++UfUiUoRLR2R1????_____Rif≈∞閉環(huán)輸入電阻Rof≈0閉環(huán)輸出電阻RifRo2．電壓并聯(lián)負(fù)反饋（反相輸入比例放大器）

在深度負(fù)反饋條件下RL?+A+UoUsF+R1R2IiIidIf????___2．電壓并聯(lián)負(fù)反饋（反相輸入比例放大器）在深度負(fù)反饋條件下由Iid≈0(虛斷)知·Ii≈If??RL?+A+UoUsF+R1R2IiIidIf????___由Iid≈0(虛斷)知·Ii≈If??RL?+A+Uo由Uid≈0(虛短)知···RL?+A+UoUsF+R1R2IiIidIf????___由Uid≈0(虛短)知···RL?+A+UoUsF+R1R········而RL?+A+UoUsF+R1R2IiIidIf????___········而RL?+A+UoUsF+R1R2IiIid故閉環(huán)互阻增益···RL?+A+UoUsF+R1R2IiIidIf????___故閉環(huán)互阻增益···RL?+A+UoUsF+R1R2IiI閉環(huán)電壓放大倍數(shù)···RL?+A+UoUsF+R1R2IiIidIf????___閉環(huán)電壓放大倍數(shù)···RL?+A+UoUsF+R1R2IiI輸入電阻RifRL?+A+UoUsF+R1R2IiIidIf????___輸入電阻RifRL?+A+UoUsF+R1R2IiIidIf輸出電阻RofRL?+A+UoUsF+R1R2IiIidIf????___輸出電阻RofRL?+A+UoUsF+R1R2IiIidIf3．電流串聯(lián)負(fù)反饋——電壓電流變換器由于····+A+Uid+++UfUiUoRLR????Io?F_____3．電流串聯(lián)負(fù)反饋——電壓電流變換器由于····+A+U故電路的閉環(huán)互導(dǎo)增益·······+A+Uid+++UfUiUoRLR????Io?F_____故電路的閉環(huán)互導(dǎo)增益·······+A+Uid+++UfUi閉環(huán)電壓放大倍數(shù)······+A+Uid+++UfUiUoRLR????Io?F_____閉環(huán)電壓放大倍數(shù)······+A+Uid+++UfUiUoR輸入、輸出電阻RifRof+A+Uid+++UfUiUoRLR????Io?F_____輸入、輸出電阻RifRof+A+Uid+++UfUiUoRL4．電流并聯(lián)負(fù)反饋——電流放大器在深度負(fù)反饋的條件下Ii≈If··Ui≈0·+A+UoUi+F+R1R2R3???????____RL4．電流并聯(lián)負(fù)反饋——電流放大器在深度負(fù)反饋的條件下Ii輸入電流··反饋電流··+A+UoUi+F+R1R2R3???????____RL輸入電流··反饋電流··+A+UoUi+F+R1R2R3??閉環(huán)電流放大倍數(shù)·······+A+UoUi+F+R1R2R3???????____RL閉環(huán)電流放大倍數(shù)·······+A+UoUi+F+R1R2R閉環(huán)電壓放大倍數(shù)······+A+UoUi+F+R1R2R3???????____RL閉環(huán)電壓放大倍數(shù)······+A+UoUi+F+R1R2R3輸入、輸出電阻RifRof+A+UoUi+F+R1R2R3???????____RL輸入、輸出電阻RifRof+A+UoUi+F+R1R2R3?1．電壓串聯(lián)負(fù)反饋5.3.3分立元件組成的反饋電路F++–+VCCT1++T2+++–+––+1．電壓串聯(lián)負(fù)反饋5.3.3分立元件組成的反饋電路F+⊕⊕⊕(1)負(fù)反饋的判斷F++–+VCCT1++T2+++–+––+⊕⊕⊕(1)負(fù)反饋的判斷F++–+VCCT1++T2+++(2)閉環(huán)電壓放大倍數(shù)··由于F++–+VCCT1++T2+++–+––+(2)閉環(huán)電壓放大倍數(shù)··由于F++–+VCCT1++T·····F++–+VCCT1++T2+++–+––+·····F++–+VCCT1++T2+++–+––+(3)輸入電阻RifF++–+VCCT1++T2+++–+––+(3)輸入電阻RifF++–+VCCT1++T2+++–(4)輸出電阻RofF++–+VCCT1++T2+++–+––+(4)輸出電阻RofF++–+VCCT1++T2+++–2．電流并聯(lián)負(fù)反饋++VCCT1+T2+F–+++––2．電流并聯(lián)負(fù)反饋++VCCT1+T2+F–+++––⊕(1)負(fù)反饋的判斷++VCCT1+T2+F–+++––⊕(1)負(fù)反饋的判斷++VCCT1+T2+F–+++––由于反饋電流iF來(lái)自于輸出級(jí)晶體管T2集電極電流iC2故電路穩(wěn)定的是iC2，而不是負(fù)載電流iOiC2iE2iO++VCCT1+T2+F–+++––由于反饋電流iF來(lái)自于輸出級(jí)晶體管T2集電極電流iC2故(2)閉環(huán)電流放大倍數(shù)·····FiC2iE2iO++VCCT1+T2+–+++––(2)閉環(huán)電流放大倍數(shù)·····FiC2iE2iO++V(3)閉環(huán)電壓放大倍數(shù)······iC2iE2iO++VCCT1+T2+F–+++––(3)閉環(huán)電壓放大倍數(shù)······iC2iE2iO++V(4)輸入電阻RifR'ifiC2iE2iO++VCCT1+T2+F–+++––(4)輸入電阻RifR'ifiC2iE2iO++VCC(5)