场效电晶体放大器网路的设计.ppt课件

Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,*,Boylestad and Nashelsky,Electronic Devices and Circuit Theory,Copyright 2006 by Pearson Education,Inc.Upper Saddle River,New Jersey 07458All rights reserved.,8-12,場效電晶體放大器網路的設計,1,設計,：,使用,近似方程式設計,。-因,R,被標準電阻值取代。,利用,完整方程式來加以測試及修改,。,注意,：1.,直流參數 對 交流響應 有很大影響。,2.,I,G,0A,R,G,在,回授組態,中以,短路等效,所取代。,因,R,G,介於,V,o,與,V,i,間，以,高阻抗,來取代。,3.,電路中各種參數對直流和交流準位所產生的影響是多方面的。,須取平衡點,問題,：,已知,V,DD,FET,種類,f,C,1,C,2,C,S,等。,要求,A,V,Z,i,Z,o,等值,。,求 電阻性元件之值。,Boylestad and NashelskyElectr,1,解：,A,V,=,g,m,(,r,d,R,D,)=,10,r,d,=1,/,y,os,=,1,/,20,S=50k,I,G,0,A,V,R,G,=,0(短路),G,接地,V,GS,Q,=0,V,直流,分析,Boylestad and Nashelsky,Electronic Devices and Circuit Theory,Copyright 2006 by Pearson Education,Inc.Upper Saddle River,New Jersey 07458All rights reserved.,2,例題 8.13：,設計下圖的固定偏壓電路,，,使其交流增益為10,，,亦即計算電阻,R,D,值。,8-12,場效電晶體放大器網路的設計,G,.,S,D,(標準值,R,D,=,2,k,),解：AV =gm(rdRD)=10 直流Boyl,2,3,Boylestad and Nashelsky,Electronic Devices and Circuit Theory,Copyright 2006 by Pearson Education,Inc.Upper Saddle River,New Jersey 07458All rights reserved.,解：,另可求,直流分析,V,DS,Q,=,V,DD,I,D,Q,R,D,=30,V,10mA2k,=10V,(,V,GS,Q,=0,V,I,D,Q,=,I,DSS,=10,mA,),交流分析,Z,i,=,R,G,=,10M,Z,o,=,r,d,/,R,D,=,50k/,2k,=,100k,2,/,52k,=1.923k,R,D,=,2k,8-12,場效電晶體放大器網路的設計,R,D,r,d,10M,50k,2k,5mS,V,gs,3Boylestad and NashelskyElect,3,解：,說明,1.為,R,S,被旁路之自偏壓組態,AC,分析-無,R,S,，,公式,同固定偏壓,2.,R,D,求法同上題，,R,S,由,DC,分析求,V,GS,Q,=,V,P,=(,4V,)=,1V,I,G,0,A,V,R,G,=,0(短路),KVL:,V,GS,Q,I,D,Q,R,S,=0,V,R,S,=,V,GS,Q,/,I,D,Q,=,(,1V,),/,5.625,mA,=,177.8,(標準值,R,S,=,180,),A,V,=,g,m,(,r,d,R,D,)=,8,r,d,=1,/,y,os,=,1,/,20,S=50k,工作點,直流分析,交流分析,Boylestad and Nashelsky,Electronic Devices and Circuit Theory,Copyright 2006 by Pearson Education,Inc.Upper Saddle River,New Jersey 07458All rights reserved.,4,8-12,場效電晶體放大器網路的設計,G,S,D,例題 8.14：,在下圖的網路中選取適當的,R,D,和,R,S,值使其增益為 8,，,在此裝置,中使用,g,m,的相對高值，並定義,V,GS,Q,=,V,P,。,解：說明1.為RS被旁路之自偏壓組態 AC分析-無,4,5,Boylestad and Nashelsky,Electronic Devices and Circuit Theory,Copyright 2006 by Pearson Education,Inc.Upper Saddle River,New Jersey 07458All rights reserved.,8-12,場效電晶體放大器網路的設計,R,D,r,d,10M,50k,?,3.75mS,V,gs,解：,(標準值,R,D,=,2.2,k,),5Boylestad and NashelskyElect,5,Boylestad and Nashelsky,Electronic Devices and Circuit Theory,Copyright 2006 by Pearson Education,Inc.Upper Saddle River,New Jersey 07458All rights reserved.,6,8-12,場效電晶體放大器網路的設計,G,S,D,例題 8.15：,若把,C,S,去除，重新計算上題電路中的,R,D,和,R,S,使其增益為 8。,解：,直流分析不變,V,GS,Q,=,1V,，,I,D,Q,=,5.625mA,(參數不變,),R,S,=,177.8,(標準值,R,S,=,180,),r,d,=50k,，,g,m,=3.75mS,假設,r,d,=50k,10(,R,D,+,R,S,)=10(,?,+,180,),A,V,=,g,m,R,D,/,(,1+,g,m,R,S,)=,8,r,d,10(,R,D,+,R,S,),50k,10(3.6k+,0.18,k)=37.8k,滿足假設,工作點,交流分析-,R,S,未旁路,(標準值,R,D,=,3.6,k,),驗算,Boylestad and NashelskyElectr,6,Boylestad and Nashelsky,Electronic Devices and Circuit Theory,Copyright 2006 by Pearson Education,Inc.Upper Saddle River,New Jersey 07458All rights reserved.,8-13,摘要表,7,p50p51,表 提供各種,常用電路組態,之,重要參數,的,正確與近似方程式,。,8-14,R,L,與,R,sig,的效應,(與,BJT,相似),討論有關 信號源電阻 與 負載電阻 對 放大器的 交流增益 之影響。,分析方法：法一代入交流模型，執行相似於無負載情況之詳細分析,法二應用 雙埠方程式,重要方程式：,、,增益,之 重要結論：,A,V,(max,),=,A,V,NL,A,V,A,v,s,大部分 共通的組態 結果 示於,p55,表8.2,Boylestad and NashelskyElectr,7,Boylestad and Nashelsky,Electronic Devices and Circuit Theory,Copyright 2006 by Pearson Education,Inc.Upper Saddle River,New Jersey 07458All rights reserved.,8-14,R,L,與,R,sig,的效應,(與,BJT,相似),8,步驟,：,1.,旁帶電容器,C,1,和,C,2,：,把直流與輸入訊號及負載分開；,X,C,=,1/,(2,fc,),R,sig,r,d,(,R,D,/,R,L,),Boylestad and NashelskyElectr,9,戴維寧,Boylestad and Nashelsky,Electronic Devices and Circuit Theory,Copyright 2006 by Pearson Education,Inc.Upper Saddle River,New Jersey 07458All rights reserved.,8-14,R,L,與,R,sig,的效應,(與,BJT,相似),10,推導,(自偏壓組態 具旁路,R,S,),：,法二,應用 雙埠研究法,其中,R,o,=,Z,o,=,r,d,/,R,D,原理,雙埠系統研究法,雙埠系統：,E,Th,=,V,o,(輸出端間開路電壓,),A,V,NL,=,V,o,/,V,i,V,o,=,A,V,NL,V,i,E,Th,=,A,V,NL,V,i,Z,Th,=,Z,o,R,o,Z,i,=,V,i,/,I,i,R,i,戴維寧 Boylestad and Nashels,10,Boylestad and Nashelsky,Electronic Devices and Circuit Theory,Copyright 2006 by Pearson Education,Inc.Upper Saddle River,New Jersey 07458All rights reserved.,8-14,R,L,與,R,sig,的效應,(與,BJT,相似),11,原理,雙埠系統研究法,雙埠系統,加上 負載,：,V,o,=,A,V,NL,V,i,R,L,/,(,R,o,+,R,L,),10,R,2,=,47k,V,B,=,V,DC,R,2,/,(,R,1,R,2,),=,20V,4.7k/,(,15k,+,4.7k,),=,4.77V,V,E,=,V,B,V,BE,=,4.77V0.7V,=4.07V,I,E,=,V,E,/,R,E,=,4.07V/1k,=,4.07mA,r,e,=,26mV/,I,E,=,26mV/4.07mA,=,6.39,電壓增益,輸入阻抗,輸出阻抗,近似法,G,S,D,B,E,C,R,G,R,S,R,D,R,1,R,E,R,C,R,2,V,DC,Boylestad and NashelskyElectr,16,17,Boylestad and Nashelsky,Electronic Devices and Circuit Theory,Copyright 2006 by Pearson Education,Inc.Upper Saddle River,New Jersey 07458All rights reserved.,8-15,串接組態,解：,Z,i,2,=,R,1,/,R,2,/,r,e,=,15k/4.7k/(2006.39),=,0.94k,g,m,=,2.64mS,A,V,1,=,g,m,(,R,D,/,Z,i,2,)=,2.64mS,(,2.4k/,0.94k,),=,1.783,A,V,2,=,R,C,/,r,e,=,2.2k/,6.39=,344.288,A,V,=,A,V,1,A,V,2,=(,1.783),(,344.288),=613.866,V,o,=,A,V,V,i,=,613.866,1mV,=613.866mV,0.6,V,輸出電壓,8-16,故障檢修,檢修電路 須結合 理論 以及 使用電表和示波器 去檢查該電路工作。,檢修電路基本步驟：,檢視電路板是否有任何明顯的問題,。(如:過熱,燒焦,焊接不良,鬆動,),使用直流電表,：依照修理手冊所載電路圖解 測試直流電壓。,運用交流訊號測試,：測量交流電壓