danshiyikaishiwomenkenengdoubulejieweishenmezheyangzuo
，jiupingtamendejijujingyanduiwomenlaishuoshiyuanyuanbugoudeo，dangranruguonimeiyouzhuyizhexiexijiewenti
，jinhouyoufanle

，kenengyouhuibeitamenma，“都說了多少遍了電容一定要就近擺放，放遠了起不到效果等等”，wangwangjingyangaosuwomenqishinaxielaogongchengshiyeshizhiyouyibufenrencaizhenzhengzhangwoqizhongdeaomiao，womenyikaishibuhuiyebuyongnanguo，duokankanziliaohenkuaijiunengzhangwode。

直到被罵好幾次後我們回去找相關資料，為什麼設計PCB電dian容rong要yao就jiu近jin擺bai放fang呢ne，等deng看kan了le資zi料liao後hou就jiu能neng了le解jie一yi些xie
，可ke是shi網wang上shang的de資zi料liao很hen雜za散san，很hen少shao能neng找zhao到dao一yi個ge很hen全quan方fang麵mian講jiang解jie的de。下xia麵mian這zhe些xie內nei容rong是shi我wo轉zhuan載zai的de一yi篇pian關guan於yu電dian容rong去qu耦ou半ban徑jing的de講jiang解jie，相xiang信xin你ni看kan了le之zhi後hou可ke以yi很hen牛niux的回答和避免類似問題的發生。

老師問： 為什麼去耦電容就近擺放呢？

學生答： 因為它有有效半徑哦，放的遠了失效的。 dianrongquoudeyigezhongyaowentishidianrongdequoubanjing。daduoshuziliaozhongdouhuitidaodianrongbaifangyaojinliangkaojinxinpian，duoshuziliaodoushicongjianxiaohuiludiangandejiaodulaitanzhegebaifangjuliwenti。queshi，jianxiaodianganshiyigezhongyaoyuanyin，danshihaiyouyigezhongyaodeyuanyindaduoshuziliaodoumeiyoutiji
，najiushidianrongquoubanjingwenti。ruguodianrongbaifanglixinpianguoyuan
，chaochuletadequoubanjing
，dianrongjiangshiqutadequoudezuoyong。

lijiequoubanjingzuihaodebanfajiushikaochazaoshengyuanhedianrongbuchangdianliuzhijiandexiangweiguanxi。dangxinpianduidianliudexuqiufashengbianhuashi，huizaidianyuanpingmiandeyigehenxiaodejubuquyuneichanshengdianyaraodong，dianrongyaobuchangzheyidianliu（或電壓），jiubixuxianganzhidaozhegedianyaraodong。xinhaozaijiezhizhongchuanboxuyaoyidingdeshijian
，yincicongfashengjubudianyaraodongdaodianrongganzhidaozheyiraodongzhijianyouyigeshijianyanchi。tongyang
，dianrongdebuchangdianliudaodaraodongquyexuyaoyigeyanchi。yincibiranzaochengzaoshengyuanhedianrongbuchangdianliuzhijiandexiangweishangdebuyizhi。

特定的電容，對與它自諧振頻率相同的噪聲補償效果最好
，我們以這個頻率來衡量這種相位關係。

當擾動區到電容的距離達到時
，補償電流的相位為
，和噪聲源相位剛好差180度，即完全反相。此時補償電流不再起作用，去耦作用失效，補償的能量無法 jishisongda。weilenengyouxiaochuandibuchangnengliang，yingshizaoshengyuanhebuchangdianliudexiangweichajinkenengdexiao，zuihaoshitongxiangweide。juliyuejin，xiangweichayuexiao，buchangnengliangchuandiyueduo，ruguojuliwei0，則補償能量百分之百傳遞到擾動區。這就要求噪聲源距離電容盡可能的近，要遠小於。實際應用中，這一距離最好控製在（λ/40 -λ/50）之間

，這是一個經驗數據。

例如：0.001uF陶瓷電容，如果安裝到電路板上後總的寄生電感為1.6nH，那麼其安裝後的諧振頻率為125.8MHz
，諧振周期為7.95ps。假設信號在電路板上的傳播速度為166ps/inch，則波長為47.9英寸。電容去耦半徑為47.9/50=0.958英寸，大約等於2.4厘米。

本例中的電容隻能對它周圍2.4厘米範圍內的電源噪聲進行補償
，即它的去耦半徑2.4limi。butongdedianrong，xiezhenpinlvbutong，quoubanjingyebutong。duiyudadianrong，yinweiqixiezhenpinlvhendi
，duiyingdebochangfeichangchang，yinerquoubanjinghenda
，zheyeshiweishenmewomenbutaiguanzhudadianrongzaidianlubanshangfangzhiweizhideyuanyin。duiyuxiaodianrong，yinquoubanjinghenxiao，yingjinkenengdekaojinxuyaoquoudexinpian
，zhezhengshidaduoshuziliaoshangdouhuifanfuqiangtiaode，xiaodianrongyaojinkenengjindekaojinxinpianfangzhi。