发布时间 : 星期一 文章《模拟电子技术基础》第三版习题解答第6章 放大电路中的反馈题解更新完毕开始阅读2015070aa36925c52cc58bd63186bceb18e8ed73
6.23 已知集成运放的开环差模增益Aod=2×105, 差模输入电阻rid=2MΩ,输出电阻ro=200Ω。试用方块图法分别求解图P6.23所示各电路的
A、F、Af、Rif、Rof。
图P6.23
解:图P6.23(a)所示反馈放大电路的基本放大电路如解图P6.23(a)所示,因此A、F、Af分析如下:
A??uO??iI?uO??Aod(rid∥Rf)?ui?rid∥RfF?
?iF1???uORf111?AF?1?Aod(rid∥Rf)??Aod?(rid∥Rf)?RfRfAf??Aod(rid∥Rf)1?Aod?(rid∥Rf)?1Rf
解图P6.23
Ri、Ro、Rif、Rof分别为
Ri?rid∥RfRo?ro∥Rf
Rif?
rid∥RfAod?(rid∥Rf)?1Rf1Rf?RfAod(ro∥Rf)(rid?Rf)Aodrid
Rof?ro∥RfAod?(rid∥Rf)?? 若 rid>>Rf,ro<<Rf,则
A?-AodRf,Ri?Rf,Ro?ro
Af??AodRf1?Aod
Rif?RfAod Rof?roAod整个电路的输入电阻约为(R+Rf /Aod)。
图P6.23(b)所示反馈放大电路的基本放大电路如解图P6.23(b)所示,因此A、F、Af、Rif、Rof分析如下:
Ri?rid?R∥Rf Ro?ro∥(R?Rf)uI?uId? A?rid?R∥Rfrid?uOrid?Aod?r?R∥Rfrid?R∥Rf?uId?idrid
?uO??uIF??uFR??uOR?RfridridRR??Aod??rid?R∥RfR?Rfrid?R∥RfR?Rf1?AF?1?Aod?ridrid?R∥RfAf?ridR1?Aod??rid?R∥RfR?RfAod?Rif?(rid?R∥Rf)Aod? ?A?ridRodridR?rid?R∥RfR?Rf
R?RfRof?ro∥(R?Rf)ridRAod??rid?R∥RfR?Rfro∥(R?Rf)rid?R∥RfR?Rf??AodridR ? 若rid>>R∥Rf,ro<<(R?Rf),则
Ri?rid Ro?ro A?Aod AF?Aod? Af?RR?Rf
Aod1?Aod?RR?RfArRR)?odidR?RfR?Rf?roR?Rf?AodR Rif?rid(1?Aod? Rof?ro1?Aod?RR?Rf