2024年11月22日
选频放大器
????·??ó?÷ ?????¤×÷???í????T?????????????? ????·??ó?÷???ü???à?????????????????????????ù?è??????????????????·??ó?????ù????·??ò??????????????·??ó???·??????·??òK???ù±?·??ó???·??·??òF????????·??????????ò????????·??ó?÷????????????????????×÷??????·??????·?????·??±??·???? KF=K/?¨1+FK?? ??????K=UO/Ui?????·???? F=UF/UO ??·???????
??°???RC?????????????????????¨b??????·???????F??????f??±????ú???¨?????????????±f=fo?±???òF=0???ù??????????????fo??????·??ó???·????????·???????KF=K?????±·??ó?÷??????????×??ó????×?????????fo,F???±???????????à????KF?????ì????????????????C?ò????????fo???????ü??????????????????????????????????????KF???????ì?????÷??????????·????????????????????¨??????T??????RC???????????ü??????????????×??????????????? ????????·???????T???????????ù???????è??????×èRS=0??????RL=00???ò?????????????? ????????????O=1/RC————————-1?? ?·???ò??Q=[1/2?¨1+a)]=[fo/2?÷fo.7]———2?? ?????????¨·???????????????·ù??·?±????? ———————3?? ?? =arctg1/QY ??????Y=??-?¨1/???????????§?????? ??=f/fo???à???§??????———————–4?? 2?÷fo.7?÷??°??????????í ??2?????????????¨??????????fo??????Q???ó???ò?¨???????
???·???Q???????ò?¨???????í???ò????Q???ó??????·???????T????????????????????????T????????????Q???ó????????×è??????????×è????????·??ó?÷??????±?????????±??????????????????÷?????????é·????????????????ó????????????·???????T???·???????·????????????×è???°?à??±????é????????×?????????????a?¨??????(0.1-0.2)?????????ó??Q???? ??????????????T???·????????-3?ù?????????????????? ????????????0= ?·???ò????Q= ??????Q??n???????±n=1?±???òQmax=0.25,???÷????±????????÷??·?±???????????n=0.5,?à??????????×è?
????à?????ò????n=2???à?????????????????à??????????????T???????????????????÷??????±???·?±???????????·????????? ??????????????????????·?·¨?? ????????????????RS??O??RL??OO???????±??T??????·??ó?÷???????÷??????????4?¨A?????é???????????¨ES?°RS????CS????T???????????????????±??????1/??CS???????ó???ù??F=O?????±?????????±???òCS??C2??C3?????????????±F?ü????RL/?¨RL+RS????????ZS??RL???°?ì????????????????f=fo?±??F=0???ò????F??????±??????ú??????4?¨B?????????????????????????????????? Z3??RL????????????F??·ù????????±????????????ü???à???????ú?ú???????????????????????ü???à?????? ??/2???????????????à????×÷??????????±??··??ó???·???????á??????·?????·??ú×??¤?????????????????????????ó???????·??4?¨A????RL??????????????CL????CL??×÷??????F??·ù?à????????????????4?¨B?????í?à?????±?????ú×??????????? R1C1=R2C2=RLCL=RSCS R1R2=?¨1+n??RLRS ?????????????????????????ò±???????????1??1??????????CS???í?????????????????????? ????????T??·??ó??à??????±??????·??????ò??±?????CS?òCL?????±
??F????·ù???à???????????????????ò?????? R1R2=?¨1+n)RSRL R1C1=R2C2 ±???×??????¨1????T??????·??ó?÷?±???????????????????????????±?÷?¤×÷?????????°?ì???÷???ò???? ?¨2????????×èZS?????????°????ZL???????ó??·??ò?á?÷??????????T???????????ò???ù±?·??ó???·???°?ó?????????ú???÷?ò?????ú???÷?????ú×???T?????????ó???¨3???????????????ó?????°?ì?????????á????????T??????????????·ù?????à??????·??ú±??????ò????T????????????°??????????ó??±??????????????????????????¤×÷???¨???????????????????? ??4?¨A??
??4?¨B?? ??4?¨C?? ??????T??????·??ó?÷??????·??? ??T??????·??ó?÷??????·???????±í
?? ?? ?à ???· ???? ??T·???????UF??????????Ui???±????·???·??ó?÷??????????Ui????BG1??·?????????UF?????ù????????????????·??????·?????·??±??·??????KF=K/?¨1+FK?????????±???òF=0????KF=K=×??ó???????§???±???òFK>>1????K=1/F??1 UF??Ui???±??????BG1???ù??????????????????·??????·??????????????·????±?????ó????????×èRS×????ó??·??ò??T?????ò?????????á?÷?????????????????????·??±??·?????????????·?à???? ?? ?? ?à UF???????ù±?·??ó???·????????BG1???ù??????UF±?Ui?à??????·??ó????UF??BG1??BG2??BG3????·??ó????Ui??BG2??BG3????·??ó?????·??±??·????KF=K/?¨1+
K1F?????????±?òF=0????KF=K=×??ó???????§???±???òFK1>>1????KF=K/K1<1???ò???????????§???±??×??????????????????ü±??????à???·???? ?? ?? ?à ????????Ui??????T??????±?C3R3????????????Ui??×÷????BG1????????????×÷????BG2???????????????·??±??·??±???KF=?¨1-F??K/?¨1+KF?????????±???òF=0????KF=K=×??ó???????§???±???òF.K>>1?°F??1????KF=0?????????§???±??×????????????????????????·×????????÷???é·? ???????????··??????÷??·?·¨ 1?????··??? ??5?????¨???????§????????·??ó???·????????????100?????¨????????6????????????????|KF|=70???ü?????????à????·??ó???·??BG1??BG2×é??????·??ó???·??????????Ui??·???????UF·?±????????????ù??[UF?????????÷BG4??????BG2?ù??]????×÷????????·???????????·??ó???·????????×è???í??·?????????T????????×è[??BG4????????×è]????????????????????????×èRS????T???°?ì??BG3?????????÷???ü????T????????×è???????????á???????·????????????T??????·??????????ü??·??ó???·???÷??????????CL??????·ù???à??????
?????????? ??5 2???÷??·?·¨ ????????????×è?????????ó??±????÷??????????R2?¨?òR3??·?±??????????¨??×èR??2?¨?òR??3?????????÷R??2?¨?òR??3??×é?????????÷??????R2?¨?òR3????10-20%????[?????¨??×è???ó????5%]?????ó°????ó?????????????? ??6 ?÷?????è ?¨1??°???6???·??T???????????÷??????????????100?????????????ó??2·ü?????ó·????÷?????÷R??2??R??3??±???????????×??????????¨??????????T????????Fmin=0.002?????ò?????¨??????54·?±???×???????5???·????????T????????????±???????????×ó±????????????í????????????·??????§????????·??ò??????Fmin=0.002. (2)?÷·??ó?÷???±?÷?¤×÷???? ?????ù±?·??ó???·???±??????·??ó?÷???÷???¤×÷??±????????????ù???????÷??????Rb1??Rb2??Ue3??6-7·ü?????? ?¨3???÷·??ó?÷????·????¨???·??????????BG1?ù???????????¨f=100???????÷??????·ù???????????¨?????§???????óK=UO/Ui=70????K>70???ò????Re2;·???????K< 70,??????Rc2???±??K=70?????? ?¨4????T???????÷ ??????T???????ò??T???÷×???f=100???°Fm
in??0???????ò??T??????×è??±?·??ó?÷??????×è???ó???à???ù????????T?????ó??????????????????·??????????ò???????????°?ì·??ó?÷?????????ù?????????í??????????T?????ó??K??????70?¨?ò??T×??????????§???????ò???÷???·???????¤×÷????????????T?????ó??K?ó??70???ò???÷??T????????????????·????????±???÷?óR??3????K??????70??·????±??????T?????ó??K???????ó???ò???÷????T????????Fmin??O??????????·?????????K?????????±?????±?÷??R??3??????K???ó??70?????? ???÷??????????????·???×??¤???ó???ò???×??°?×??¤?????ó?????????÷?????????à×??¤????1???????????ü??×??¤???ò????fo???ü??T?????ú?ú??·????????÷??R3??×??¤??????2???????????????ü?¨?????????±??????????T??????·ù???à???????????????????????????±??·??ó?÷???????????ò???·?????á?????????à????????????????·??????ò???????????à×??¤???????????????±??·????·?ò???????????????·??????????????????????×?????T??????·??ó?÷??????????C4???°?ì??3??????×??¤?????¨???????§????????·?·¨??????·??ó?÷???¨??????????????????????????????????5???·????
??Cm????BG2??????±???R2??Cm??????????Cm???????????????????±??Cm????×÷????????×??¤???????ü???ì????BG2??×è???????±????????????????×??¤??????