???§????

???§?????¨??????FET?????????????÷?????ü???????????????????????÷??±??????ü????????×è???????ù????????·??§?ó?????????????????????ò????·????????÷????×????·????

???????§???????á?????í?°????

???§???????á?????????¤?????á?????????á??????N??????P?????????????????? 1???á?????§?????¨JFET?? ?¨1???á?????í ?ü???á???°·???????1????N???è°?????????????D??????S???????????????è°??????à?÷×?????P????????????PN?á????P???????????????????????????¤??Go???ù????????N???????????§????

??1??N?????á???????§???????á???°·???

????PN?á???????÷×?????????????PN?ù±??????????????????????ù??????????????1?????????±????????????ED???¨?±???????¤????????????PN?á???????ù?????????????????????ò???????????????????????????????????÷ID???ú????·??????????¤???????????????????ò????±??í??ID±??ó???ù?????¤??????EG???????????????÷ID??±????????????????§???????????????????? ?¨2???????ú?? 1??×??????? ??2?¨a????????N?????á?????§???????¤??---???÷?????ú????????×????????ú?????ü????×??????????????ú??·????à?????±?¤??????VGS=0?±?????????÷????IDSS±í????VGS±????±??ID??????????ID???ü???????¤??????????????????????VP±í??????0??VGS??VP??????????ID??VGS?????????ü??±í?????? ID=IDSS?¨1-|VGS/VP|?? ??????gm????gm=?¨?÷ID/?÷VGS??|VDS=?????¨???·??| ???????÷ID------???????÷?????¨??°??? ------?÷VGS-----?¤???????????¨·ü??

??2???á?????§?????????ú??

2???????????¨?????????? ??2(b)?????????§???????????????ú?????ü???§???????????????????ú?? ???à???? ????±???×è???¨????I??????I????VDS±??????????¨??×è???¤??VGS????±???????????±???×è?????±?¤?????¨?±?????¨??×è???¨????ID??VDS?ü?????????ó???±VGS??VP?±????????????×è???ó?¨????????IP=0???±VGS=0?±????????????×è?????¨???¨????ID=IDSS???????????????§????????????×÷???? ?????÷???¨????II?????±????????VDS???????ó??VDS??|VP|?±?????????÷??IP??????±??????ó?ù±?±?????±????????????????÷???ò±?????????????????????????VGS?????????ú???ü????????????ID??VGS??????????????????????·??ó???? ???÷?????¨?????ó????????VDS????????????????????PN?á?ù??????????????±??÷???????????÷ID???????ó????????????????????×????á?????? 2???????¤???§???? ?ü??????????????????°??????ù×é?????ù????????????---??????---°????????§???????ò??MOS???§?????? ?¨1???á?????í ?ü???á?????????°·???????3?ù?????????éP??±??è??×÷?????×?????ü????????????????????N??????×÷??????S??????D?????è??±í???????????????????ó??????????????????????G?¨?¤?????????¤???????ü???????????ù???????????¤?????§??????

??3??N?????¨?????????????¤???§?????á???°·???

?????ì??×??±???¨???¤?????????????????ó??????×????????????????í???à???????????à????????????????????°???????????N?????¨????????????????????????VGS=0?±???????ó?????????÷ID???±?¤????????±??±????????±?????????????????±??????????????í??????????±????ò?????????÷ID??×??¤????????±?????±????? ???§????????×÷·????????????±?¤???????±?????ó???????÷???????????????±?¤???????????????÷????????±??????????¨???¤?????ó???????????÷?????????????? ?¨2???????ú?? 1??×????????¨?¤??----???÷?????? ??4?¨a????????N???????????????¤???§??????×????????ú????????Vp???????????¨?¤??????????????IDSS??±????????÷?? ??4?¨b????????N???????????????¤???§????×????????ú????????Vr?????????????±?¤??????????VT?±?????????÷???????????????? 2???????????¨?????????? ??5?¨a????????N???????????????¤???§???????????????ú???? ??5(b)??N???????????????¤???§???????????????ú?? ??

??4??N????MOS???§????×????????ú??

??5??N????MOS???§???????????????ú??

????????N???×P?????¨????1???????§???????à·??????????????????????? ?÷?????§???÷????·??à??????·??????÷??·ü°??????¨×???????????????????

???????§???????÷??????

1??????????VP ?±VDS?????????¨????????IDS???????????????÷?±???¤?????ù????????VGS????????????VP?? 2??±????????÷IDSS ???????¤?????·???????????????ù?????????ó??VP?±?????????÷????IDSS?? 3???÷??????BVDS ±í?????????????ù????????×??ó????????????±??????÷?????????????÷?????±??????VDS?? 4???±?÷??????×èRGS ?????¨???¤???????????¤???????????±?÷??×è???????????????÷???¤???????÷??±í?????á?????§??????RGS????1000000000?·???????¤???§??????RGS??????10000000000000?·?? 5??????????gm ???????÷????±?????????????±??????¤??????????±?????±??????????????? gm= ?÷ID/?÷VGS ?ü?????????§?????¤???????????????÷????????????????????????????·??ó×÷???????????????????é???????¤??????±???1·ü?±???????à??±????à????°??¨??A/V???ò??°??¨mA/V????±í??