【場效(xiao)應(ying)管工(gong)作(zuo)原(yuan)理】場效(xiao)應(ying)管的工(gong)作(zuo)原(yuan)理是(shi)什么 場效(xiao)應(ying)管的特點(dian)

場效應管的工作原理是什么

場效應管工作原(yuan)理(li)用一(yi)(yi)句話說，就是“漏極(ji)(ji)(ji)-源(yuan)(yuan)極(ji)(ji)(ji)間(jian)(jian)(jian)流(liu)(liu)經溝(gou)(gou)道(dao)的(de)(de)ID，用以柵極(ji)(ji)(ji)與溝(gou)(gou)道(dao)間(jian)(jian)(jian)的(de)(de)pn結形(xing)成的(de)(de)反偏(pian)的(de)(de)柵極(ji)(ji)(ji)電壓控制ID”。更正確地說，ID流(liu)(liu)經通(tong)路的(de)(de)寬(kuan)度(du)(du)，即(ji)溝(gou)(gou)道(dao)截面積，它是由pn結反偏(pian)的(de)(de)變化，產生耗盡層擴展(zhan)(zhan)變化控制的(de)(de)緣故。在VGS=0的(de)(de)非飽和區域，表示的(de)(de)過(guo)(guo)渡(du)層的(de)(de)擴展(zhan)(zhan)因為不(bu)(bu)很大，根據漏極(ji)(ji)(ji)-源(yuan)(yuan)極(ji)(ji)(ji)間(jian)(jian)(jian)所加VDS的(de)(de)電場，源(yuan)(yuan)極(ji)(ji)(ji)區域的(de)(de)某些(xie)電子被(bei)漏極(ji)(ji)(ji)拉(la)去，即(ji)從漏極(ji)(ji)(ji)向源(yuan)(yuan)極(ji)(ji)(ji)有電流(liu)(liu)ID流(liu)(liu)動(dong)。從門(men)極(ji)(ji)(ji)向漏極(ji)(ji)(ji)擴展(zhan)(zhan)的(de)(de)過(guo)(guo)度(du)(du)層將(jiang)溝(gou)(gou)道(dao)的(de)(de)一(yi)(yi)部分(fen)(fen)構成堵塞(sai)型，ID飽和。將(jiang)這(zhe)(zhe)種(zhong)狀態(tai)稱(cheng)為夾(jia)斷。這(zhe)(zhe)意味(wei)著(zhu)過(guo)(guo)渡(du)層將(jiang)溝(gou)(gou)道(dao)的(de)(de)一(yi)(yi)部分(fen)(fen)阻擋，并(bing)不(bu)(bu)是電流(liu)(liu)被(bei)切(qie)斷。

該圖片由注冊用戶"橘子de殿堂"提供，版權聲明反饋

在過渡層(ceng)由(you)于(yu)沒(mei)有電(dian)(dian)子(zi)、空穴的(de)自由(you)移動，在理想狀態(tai)下幾乎具有絕緣特性，通(tong)常電(dian)(dian)流(liu)(liu)也難流(liu)(liu)動。但是此時漏(lou)極-源極間的(de)電(dian)(dian)場(chang)(chang)(chang)，實(shi)際上是兩個過渡層(ceng)接觸(chu)漏(lou)極與(yu)門極下部(bu)附近，由(you)于(yu)漂(piao)移電(dian)(dian)場(chang)(chang)(chang)拉去的(de)高速電(dian)(dian)子(zi)通(tong)過過渡層(ceng)。因漂(piao)移電(dian)(dian)場(chang)(chang)(chang)的(de)強(qiang)度幾乎不變產(chan)生ID的(de)飽和現象。其次，VGS向負的(de)方向變化(hua)，讓(rang)VGS=VGS(off)，此時過渡層(ceng)大致成為覆蓋全區域的(de)狀態(tai)。而且VDS的(de)電(dian)(dian)場(chang)(chang)(chang)大部(bu)分加到過渡層(ceng)上，將電(dian)(dian)子(zi)拉向漂(piao)移方向的(de)電(dian)(dian)場(chang)(chang)(chang)，只(zhi)有靠近源極的(de)很短部(bu)分，這更使電(dian)(dian)流(liu)(liu)不能流(liu)(liu)通(tong)。

MOS場效應管電源開關電路

MOS場效應管也(ye)被稱(cheng)為金(jin)屬氧化物半導(dao)體場(chang)效(xiao)(xiao)應(ying)管(guan)(MetalOxideSemiconductor FieldEffect Transistor, MOSFET)。它一般有(you)耗盡型(xing)和增強(qiang)型(xing)兩種。增強(qiang)型(xing)MOS場(chang)效(xiao)(xiao)應(ying)管(guan)可分為NPN型(xing)PNP型(xing)。NPN型(xing)通常稱(cheng)為N溝道型(xing)，PNP型(xing)也(ye)叫P溝道型(xing)。對于N溝道的(de)(de)場(chang)效(xiao)(xiao)應(ying)管(guan)其(qi)源(yuan)極(ji)和漏極(ji)接在(zai)N型(xing)半導(dao)體上，同(tong)樣對于P溝道的(de)(de)場(chang)效(xiao)(xiao)應(ying)管(guan)其(qi)源(yuan)極(ji)和漏極(ji)則接在(zai)P型(xing)半導(dao)體上。場(chang)效(xiao)(xiao)應(ying)管(guan)的(de)(de)輸(shu)(shu)(shu)出電(dian)(dian)流(liu)是由輸(shu)(shu)(shu)入的(de)(de)電(dian)(dian)壓(ya)（或(huo)稱(cheng)電(dian)(dian)場(chang)）控制，可以(yi)認為輸(shu)(shu)(shu)入電(dian)(dian)流(liu)極(ji)小或(huo)沒有(you)輸(shu)(shu)(shu)入電(dian)(dian)流(liu)，這使(shi)得該(gai)器件有(you)很高的(de)(de)輸(shu)(shu)(shu)入阻抗，同(tong)時這也(ye)是我們稱(cheng)之為場(chang)效(xiao)(xiao)應(ying)管(guan)的(de)(de)原因。

在(zai)(zai)(zai)(zai)二極(ji)(ji)(ji)(ji)管(guan)加(jia)(jia)上正(zheng)向電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)（P端(duan)(duan)(duan)接(jie)正(zheng)極(ji)(ji)(ji)(ji)，N端(duan)(duan)(duan)接(jie)負(fu)極(ji)(ji)(ji)(ji)）時(shi)(shi)(shi)(shi)，二極(ji)(ji)(ji)(ji)管(guan)導通，其PN結有電(dian)(dian)(dian)(dian)流通過。這(zhe)是因為在(zai)(zai)(zai)(zai)P型(xing)(xing)(xing)(xing)半(ban)(ban)導體(ti)(ti)端(duan)(duan)(duan)為正(zheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)時(shi)(shi)(shi)(shi)，N型(xing)(xing)(xing)(xing)半(ban)(ban)導體(ti)(ti)內(nei)的(de)(de)(de)(de)負(fu)電(dian)(dian)(dian)(dian)子被吸引(yin)而(er)涌向加(jia)(jia)有正(zheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)的(de)(de)(de)(de)P型(xing)(xing)(xing)(xing)半(ban)(ban)導體(ti)(ti)端(duan)(duan)(duan)，而(er)P型(xing)(xing)(xing)(xing)半(ban)(ban)導體(ti)(ti)端(duan)(duan)(duan)內(nei)的(de)(de)(de)(de)正(zheng)電(dian)(dian)(dian)(dian)子則(ze)朝N型(xing)(xing)(xing)(xing)半(ban)(ban)導體(ti)(ti)端(duan)(duan)(duan)運動(dong)，從(cong)而(er)形成(cheng)導通電(dian)(dian)(dian)(dian)流。同(tong)理，當(dang)(dang)二極(ji)(ji)(ji)(ji)管(guan)加(jia)(jia)上反向電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)（P端(duan)(duan)(duan)接(jie)負(fu)極(ji)(ji)(ji)(ji)，N端(duan)(duan)(duan)接(jie)正(zheng)極(ji)(ji)(ji)(ji)）時(shi)(shi)(shi)(shi)，這(zhe)時(shi)(shi)(shi)(shi)在(zai)(zai)(zai)(zai)P型(xing)(xing)(xing)(xing)半(ban)(ban)導體(ti)(ti)端(duan)(duan)(duan)為負(fu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)，正(zheng)電(dian)(dian)(dian)(dian)子被聚(ju)集(ji)(ji)在(zai)(zai)(zai)(zai)P型(xing)(xing)(xing)(xing)半(ban)(ban)導體(ti)(ti)端(duan)(duan)(duan)，負(fu)電(dian)(dian)(dian)(dian)子則(ze)聚(ju)集(ji)(ji)在(zai)(zai)(zai)(zai)N型(xing)(xing)(xing)(xing)半(ban)(ban)導體(ti)(ti)端(duan)(duan)(duan)，電(dian)(dian)(dian)(dian)子不(bu)移動(dong)，其PN結沒有電(dian)(dian)(dian)(dian)流通過，二極(ji)(ji)(ji)(ji)管(guan)截止。在(zai)(zai)(zai)(zai)柵極(ji)(ji)(ji)(ji)沒有電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)時(shi)(shi)(shi)(shi)，由(you)前面(mian)分(fen)析可知(zhi)，在(zai)(zai)(zai)(zai)源(yuan)極(ji)(ji)(ji)(ji)與(yu)漏(lou)(lou)(lou)極(ji)(ji)(ji)(ji)之(zhi)間不(bu)會有電(dian)(dian)(dian)(dian)流流過，此時(shi)(shi)(shi)(shi)場效(xiao)應(ying)管(guan)處與(yu)截止狀態（圖7a）。當(dang)(dang)有一(yi)個正(zheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)加(jia)(jia)在(zai)(zai)(zai)(zai)N溝(gou)道(dao)的(de)(de)(de)(de)MOS場效(xiao)應(ying)管(guan)柵極(ji)(ji)(ji)(ji)上時(shi)(shi)(shi)(shi)，由(you)于電(dian)(dian)(dian)(dian)場的(de)(de)(de)(de)作用，此時(shi)(shi)(shi)(shi)N型(xing)(xing)(xing)(xing)半(ban)(ban)導體(ti)(ti)的(de)(de)(de)(de)源(yuan)極(ji)(ji)(ji)(ji)和(he)漏(lou)(lou)(lou)極(ji)(ji)(ji)(ji)的(de)(de)(de)(de)負(fu)電(dian)(dian)(dian)(dian)子被吸引(yin)出來(lai)而(er)涌向柵極(ji)(ji)(ji)(ji)，但由(you)于氧化(hua)膜(mo)的(de)(de)(de)(de)阻擋，使(shi)得(de)電(dian)(dian)(dian)(dian)子聚(ju)集(ji)(ji)在(zai)(zai)(zai)(zai)兩個N溝(gou)道(dao)之(zhi)間的(de)(de)(de)(de)P型(xing)(xing)(xing)(xing)半(ban)(ban)導體(ti)(ti)中（見圖7b），從(cong)而(er)形成(cheng)電(dian)(dian)(dian)(dian)流，使(shi)源(yuan)極(ji)(ji)(ji)(ji)和(he)漏(lou)(lou)(lou)極(ji)(ji)(ji)(ji)之(zhi)間導通。可以想像為兩個N型(xing)(xing)(xing)(xing)半(ban)(ban)導體(ti)(ti)之(zhi)間為一(yi)條溝(gou)，柵極(ji)(ji)(ji)(ji)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)的(de)(de)(de)(de)建立相當(dang)(dang)于為它(ta)們之(zhi)間搭了(le)一(yi)座橋(qiao)梁，該橋(qiao)的(de)(de)(de)(de)大小(xiao)由(you)柵壓(ya)(ya)(ya)(ya)(ya)的(de)(de)(de)(de)大小(xiao)決定。

C-MOS場效應管

電路將一個增強型P溝道MOS場效應管和一個增強型N溝道MOS場效應管組合在(zai)(zai)(zai)(zai)一起使(shi)用(yong)。當輸入(ru)端(duan)(duan)為(wei)低電(dian)(dian)(dian)平時，P溝道MOS場(chang)(chang)效(xiao)(xiao)應(ying)(ying)管(guan)(guan)導(dao)通(tong)(tong)，輸出(chu)端(duan)(duan)與(yu)電(dian)(dian)(dian)源(yuan)(yuan)正極(ji)接通(tong)(tong)。當輸入(ru)端(duan)(duan)為(wei)高電(dian)(dian)(dian)平時，N溝道MOS場(chang)(chang)效(xiao)(xiao)應(ying)(ying)管(guan)(guan)導(dao)通(tong)(tong)，輸出(chu)端(duan)(duan)與(yu)電(dian)(dian)(dian)源(yuan)(yuan)地接通(tong)(tong)。在(zai)(zai)(zai)(zai)該(gai)電(dian)(dian)(dian)路中，P溝道MOS場(chang)(chang)效(xiao)(xiao)應(ying)(ying)管(guan)(guan)和N溝道MOS場(chang)(chang)效(xiao)(xiao)應(ying)(ying)管(guan)(guan)總是在(zai)(zai)(zai)(zai)相(xiang)反的狀(zhuang)態(tai)下(xia)工作(zuo)，其(qi)相(xiang)位輸入(ru)端(duan)(duan)和輸出(chu)端(duan)(duan)相(xiang)反。通(tong)(tong)過這(zhe)種工作(zuo)方式我們可以獲得較大(da)的電(dian)(dian)(dian)流輸出(chu)。同時由于漏電(dian)(dian)(dian)流的影響，使(shi)得柵(zha)(zha)壓(ya)在(zai)(zai)(zai)(zai)還沒(mei)有到(dao)0V，通(tong)(tong)常(chang)在(zai)(zai)(zai)(zai)柵(zha)(zha)極(ji)電(dian)(dian)(dian)壓(ya)小于1到(dao)2V時，MOS場(chang)(chang)效(xiao)(xiao)應(ying)(ying)管(guan)(guan)既被關斷(duan)。不(bu)同場(chang)(chang)效(xiao)(xiao)應(ying)(ying)管(guan)(guan)其(qi)關斷(duan)電(dian)(dian)(dian)壓(ya)略有不(bu)同。也正因(yin)為(wei)如此，使(shi)得該(gai)電(dian)(dian)(dian)路不(bu)會因(yin)為(wei)兩管(guan)(guan)同時導(dao)通(tong)(tong)而造成電(dian)(dian)(dian)源(yuan)(yuan)短路。

場效應管的特點

（1）場效應管(guan)是(shi)電(dian)壓控制器件(jian)，它通(tong)過(guo)VGS(柵源電(dian)壓)來控制ID（漏極(ji)電(dian)流(liu)）；

（2）場效應管的(de)控(kong)制輸入(ru)端電(dian)流(liu)極小，因此它的(de)輸入(ru)電(dian)阻（107～1012Ω）很大。

（3）它(ta)(ta)是利用多數載流(liu)子導電，因此(ci)它(ta)(ta)的溫度穩(wen)定性較好(hao)；

（4）它組成(cheng)的放大(da)電路的電壓(ya)放大(da)系數(shu)要小于三(san)極管組成(cheng)放大(da)電路的電壓(ya)放大(da)系數(shu)；

（5）場效應管的抗輻射能(neng)力強；

（6）由于它不(bu)存在(zai)雜亂運動的電子擴(kuo)散(san)引起的散(san)粒噪聲，所以(yi)噪聲低。