【場(chang)(chang)效應管工(gong)作原理】場(chang)(chang)效應管的(de)工(gong)作原理是什么(me) 場(chang)(chang)效應管的(de)特點

場效應管的工作原理是什么

場效應管工作原理用一句話說，就是(shi)“漏(lou)(lou)極(ji)(ji)(ji)(ji)-源(yuan)極(ji)(ji)(ji)(ji)間流(liu)經溝(gou)道(dao)的(de)(de)(de)ID，用以柵極(ji)(ji)(ji)(ji)與溝(gou)道(dao)間的(de)(de)(de)pn結形成的(de)(de)(de)反偏的(de)(de)(de)柵極(ji)(ji)(ji)(ji)電(dian)壓控制ID”。更(geng)正確地說，ID流(liu)經通(tong)路的(de)(de)(de)寬度，即(ji)溝(gou)道(dao)截(jie)面積，它是(shi)由pn結反偏的(de)(de)(de)變化，產生耗盡層(ceng)擴展(zhan)變化控制的(de)(de)(de)緣故。在VGS=0的(de)(de)(de)非飽和(he)區域(yu)，表示的(de)(de)(de)過渡層(ceng)的(de)(de)(de)擴展(zhan)因為不很大(da)，根據漏(lou)(lou)極(ji)(ji)(ji)(ji)-源(yuan)極(ji)(ji)(ji)(ji)間所加VDS的(de)(de)(de)電(dian)場(chang)，源(yuan)極(ji)(ji)(ji)(ji)區域(yu)的(de)(de)(de)某些(xie)電(dian)子被漏(lou)(lou)極(ji)(ji)(ji)(ji)拉去(qu)，即(ji)從(cong)漏(lou)(lou)極(ji)(ji)(ji)(ji)向(xiang)源(yuan)極(ji)(ji)(ji)(ji)有電(dian)流(liu)ID流(liu)動。從(cong)門極(ji)(ji)(ji)(ji)向(xiang)漏(lou)(lou)極(ji)(ji)(ji)(ji)擴展(zhan)的(de)(de)(de)過度層(ceng)將(jiang)(jiang)溝(gou)道(dao)的(de)(de)(de)一部分(fen)構成堵塞型，ID飽和(he)。將(jiang)(jiang)這種狀態(tai)稱(cheng)為夾斷。這意味著過渡層(ceng)將(jiang)(jiang)溝(gou)道(dao)的(de)(de)(de)一部分(fen)阻擋，并不是(shi)電(dian)流(liu)被切斷。

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在過(guo)(guo)渡層(ceng)由于(yu)沒有(you)電(dian)(dian)(dian)子(zi)、空(kong)穴(xue)的(de)自(zi)由移(yi)動，在理(li)想狀態下幾乎(hu)具有(you)絕緣(yuan)特性，通(tong)(tong)常電(dian)(dian)(dian)流也難(nan)流動。但是此時漏(lou)極(ji)-源極(ji)間的(de)電(dian)(dian)(dian)場，實際上是兩個(ge)過(guo)(guo)渡層(ceng)接觸漏(lou)極(ji)與門極(ji)下部(bu)附近，由于(yu)漂(piao)移(yi)電(dian)(dian)(dian)場拉去的(de)高(gao)速電(dian)(dian)(dian)子(zi)通(tong)(tong)過(guo)(guo)過(guo)(guo)渡層(ceng)。因(yin)漂(piao)移(yi)電(dian)(dian)(dian)場的(de)強度幾乎(hu)不(bu)變產生ID的(de)飽和現象。其(qi)次，VGS向(xiang)負的(de)方(fang)向(xiang)變化，讓VGS=VGS(off)，此時過(guo)(guo)渡層(ceng)大致成為覆蓋全(quan)區(qu)域的(de)狀態。而且VDS的(de)電(dian)(dian)(dian)場大部(bu)分加到(dao)過(guo)(guo)渡層(ceng)上，將電(dian)(dian)(dian)子(zi)拉向(xiang)漂(piao)移(yi)方(fang)向(xiang)的(de)電(dian)(dian)(dian)場，只有(you)靠近源極(ji)的(de)很短(duan)部(bu)分，這更(geng)使電(dian)(dian)(dian)流不(bu)能流通(tong)(tong)。

MOS場效應管電源開關電路

MOS場效應管也(ye)被稱(cheng)為(wei)金屬氧化(hua)物半導(dao)體場(chang)(chang)(chang)效(xiao)應(ying)管(guan)(guan)(guan)(MetalOxideSemiconductor FieldEffect Transistor, MOSFET)。它一般有耗盡型(xing)(xing)(xing)(xing)和增強型(xing)(xing)(xing)(xing)兩種。增強型(xing)(xing)(xing)(xing)MOS場(chang)(chang)(chang)效(xiao)應(ying)管(guan)(guan)(guan)可分為(wei)NPN型(xing)(xing)(xing)(xing)PNP型(xing)(xing)(xing)(xing)。NPN型(xing)(xing)(xing)(xing)通(tong)常(chang)稱(cheng)為(wei)N溝道(dao)(dao)(dao)型(xing)(xing)(xing)(xing)，PNP型(xing)(xing)(xing)(xing)也(ye)叫(jiao)P溝道(dao)(dao)(dao)型(xing)(xing)(xing)(xing)。對于N溝道(dao)(dao)(dao)的(de)(de)場(chang)(chang)(chang)效(xiao)應(ying)管(guan)(guan)(guan)其源(yuan)極(ji)(ji)和漏(lou)極(ji)(ji)接在(zai)(zai)N型(xing)(xing)(xing)(xing)半導(dao)體上(shang)，同樣對于P溝道(dao)(dao)(dao)的(de)(de)場(chang)(chang)(chang)效(xiao)應(ying)管(guan)(guan)(guan)其源(yuan)極(ji)(ji)和漏(lou)極(ji)(ji)則接在(zai)(zai)P型(xing)(xing)(xing)(xing)半導(dao)體上(shang)。場(chang)(chang)(chang)效(xiao)應(ying)管(guan)(guan)(guan)的(de)(de)輸(shu)出電(dian)流是由輸(shu)入(ru)的(de)(de)電(dian)壓（或(huo)稱(cheng)電(dian)場(chang)(chang)(chang)）控(kong)制，可以(yi)認為(wei)輸(shu)入(ru)電(dian)流極(ji)(ji)小(xiao)或(huo)沒有輸(shu)入(ru)電(dian)流，這(zhe)使(shi)得(de)該器件有很高的(de)(de)輸(shu)入(ru)阻抗，同時這(zhe)也(ye)是我們稱(cheng)之(zhi)為(wei)場(chang)(chang)(chang)效(xiao)應(ying)管(guan)(guan)(guan)的(de)(de)原因。

在(zai)(zai)二極(ji)(ji)(ji)(ji)管(guan)(guan)加上正(zheng)(zheng)(zheng)向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)（P端(duan)(duan)接(jie)(jie)(jie)正(zheng)(zheng)(zheng)極(ji)(ji)(ji)(ji)，N端(duan)(duan)接(jie)(jie)(jie)負(fu)極(ji)(ji)(ji)(ji)）時(shi)，二極(ji)(ji)(ji)(ji)管(guan)(guan)導(dao)(dao)通(tong)(tong)，其(qi)PN結(jie)有電(dian)(dian)(dian)(dian)流通(tong)(tong)過(guo)(guo)。這是(shi)因為(wei)(wei)(wei)在(zai)(zai)P型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)導(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)為(wei)(wei)(wei)正(zheng)(zheng)(zheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)時(shi)，N型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)導(dao)(dao)體(ti)(ti)(ti)(ti)內的(de)(de)負(fu)電(dian)(dian)(dian)(dian)子(zi)(zi)被(bei)吸(xi)引(yin)而(er)(er)涌向(xiang)加有正(zheng)(zheng)(zheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)(de)P型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)導(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)，而(er)(er)P型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)導(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)內的(de)(de)正(zheng)(zheng)(zheng)電(dian)(dian)(dian)(dian)子(zi)(zi)則朝N型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)導(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)運動，從(cong)而(er)(er)形(xing)成導(dao)(dao)通(tong)(tong)電(dian)(dian)(dian)(dian)流。同理，當二極(ji)(ji)(ji)(ji)管(guan)(guan)加上反(fan)向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)（P端(duan)(duan)接(jie)(jie)(jie)負(fu)極(ji)(ji)(ji)(ji)，N端(duan)(duan)接(jie)(jie)(jie)正(zheng)(zheng)(zheng)極(ji)(ji)(ji)(ji)）時(shi)，這時(shi)在(zai)(zai)P型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)導(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)為(wei)(wei)(wei)負(fu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，正(zheng)(zheng)(zheng)電(dian)(dian)(dian)(dian)子(zi)(zi)被(bei)聚(ju)集在(zai)(zai)P型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)導(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)，負(fu)電(dian)(dian)(dian)(dian)子(zi)(zi)則聚(ju)集在(zai)(zai)N型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)導(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)，電(dian)(dian)(dian)(dian)子(zi)(zi)不移動，其(qi)PN結(jie)沒(mei)有電(dian)(dian)(dian)(dian)流通(tong)(tong)過(guo)(guo)，二極(ji)(ji)(ji)(ji)管(guan)(guan)截止(zhi)。在(zai)(zai)柵(zha)極(ji)(ji)(ji)(ji)沒(mei)有電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)時(shi)，由(you)(you)(you)前(qian)面(mian)分析(xi)可知，在(zai)(zai)源(yuan)極(ji)(ji)(ji)(ji)與漏極(ji)(ji)(ji)(ji)之(zhi)間不會有電(dian)(dian)(dian)(dian)流流過(guo)(guo)，此時(shi)場(chang)效應(ying)管(guan)(guan)處與截止(zhi)狀態（圖7a）。當有一(yi)個(ge)正(zheng)(zheng)(zheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)加在(zai)(zai)N溝道的(de)(de)MOS場(chang)效應(ying)管(guan)(guan)柵(zha)極(ji)(ji)(ji)(ji)上時(shi)，由(you)(you)(you)于電(dian)(dian)(dian)(dian)場(chang)的(de)(de)作用，此時(shi)N型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)導(dao)(dao)體(ti)(ti)(ti)(ti)的(de)(de)源(yuan)極(ji)(ji)(ji)(ji)和(he)(he)漏極(ji)(ji)(ji)(ji)的(de)(de)負(fu)電(dian)(dian)(dian)(dian)子(zi)(zi)被(bei)吸(xi)引(yin)出來而(er)(er)涌向(xiang)柵(zha)極(ji)(ji)(ji)(ji)，但由(you)(you)(you)于氧化(hua)膜的(de)(de)阻(zu)擋，使得電(dian)(dian)(dian)(dian)子(zi)(zi)聚(ju)集在(zai)(zai)兩(liang)個(ge)N溝道之(zhi)間的(de)(de)P型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)導(dao)(dao)體(ti)(ti)(ti)(ti)中（見圖7b），從(cong)而(er)(er)形(xing)成電(dian)(dian)(dian)(dian)流，使源(yuan)極(ji)(ji)(ji)(ji)和(he)(he)漏極(ji)(ji)(ji)(ji)之(zhi)間導(dao)(dao)通(tong)(tong)。可以想(xiang)像為(wei)(wei)(wei)兩(liang)個(ge)N型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)導(dao)(dao)體(ti)(ti)(ti)(ti)之(zhi)間為(wei)(wei)(wei)一(yi)條溝，柵(zha)極(ji)(ji)(ji)(ji)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)(de)建立相當于為(wei)(wei)(wei)它們之(zhi)間搭了(le)一(yi)座橋(qiao)梁，該橋(qiao)的(de)(de)大(da)小(xiao)(xiao)由(you)(you)(you)柵(zha)壓(ya)(ya)(ya)的(de)(de)大(da)小(xiao)(xiao)決(jue)定(ding)。

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(he)在(zai)(zai)一(yi)起使(shi)用。當(dang)輸(shu)入(ru)端(duan)(duan)為低電(dian)(dian)(dian)(dian)平時(shi)，P溝道(dao)MOS場(chang)(chang)(chang)效應(ying)管導通(tong)(tong)，輸(shu)出(chu)端(duan)(duan)與電(dian)(dian)(dian)(dian)源正(zheng)極(ji)接通(tong)(tong)。當(dang)輸(shu)入(ru)端(duan)(duan)為高電(dian)(dian)(dian)(dian)平時(shi)，N溝道(dao)MOS場(chang)(chang)(chang)效應(ying)管導通(tong)(tong)，輸(shu)出(chu)端(duan)(duan)與電(dian)(dian)(dian)(dian)源地(di)接通(tong)(tong)。在(zai)(zai)該電(dian)(dian)(dian)(dian)路中，P溝道(dao)MOS場(chang)(chang)(chang)效應(ying)管和(he)(he)N溝道(dao)MOS場(chang)(chang)(chang)效應(ying)管總(zong)是在(zai)(zai)相反(fan)的狀(zhuang)態(tai)下工作(zuo)，其(qi)相位輸(shu)入(ru)端(duan)(duan)和(he)(he)輸(shu)出(chu)端(duan)(duan)相反(fan)。通(tong)(tong)過這種工作(zuo)方式我們可以獲得較大的電(dian)(dian)(dian)(dian)流(liu)輸(shu)出(chu)。同時(shi)由于漏電(dian)(dian)(dian)(dian)流(liu)的影響，使(shi)得柵壓(ya)在(zai)(zai)還沒有到0V，通(tong)(tong)常(chang)在(zai)(zai)柵極(ji)電(dian)(dian)(dian)(dian)壓(ya)小于1到2V時(shi)，MOS場(chang)(chang)(chang)效應(ying)管既被關斷。不(bu)同場(chang)(chang)(chang)效應(ying)管其(qi)關斷電(dian)(dian)(dian)(dian)壓(ya)略有不(bu)同。也(ye)正(zheng)因為如此，使(shi)得該電(dian)(dian)(dian)(dian)路不(bu)會因為兩管同時(shi)導通(tong)(tong)而造成(cheng)電(dian)(dian)(dian)(dian)源短路。

場效應管的特點

（1）場效應管是電壓控制器(qi)件(jian)，它(ta)通過VGS(柵源電壓)來控制ID（漏極電流）；

（2）場效應(ying)管的控制輸入(ru)端電(dian)流極小，因此它的輸入(ru)電(dian)阻（107～1012Ω）很大(da)。

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

（4）它(ta)組成的放(fang)(fang)大電路的電壓(ya)放(fang)(fang)大系(xi)數要小(xiao)于(yu)三極管(guan)組成放(fang)(fang)大電路的電壓(ya)放(fang)(fang)大系(xi)數；

（5）場效應管的抗輻射能(neng)力強；

（6）由于它不存在(zai)雜亂運動的電子(zi)擴散引起的散粒噪聲，所(suo)以(yi)噪聲低。