【場(chang)效(xiao)應(ying)管工(gong)作(zuo)原(yuan)理】場(chang)效(xiao)應(ying)管的工(gong)作(zuo)原(yuan)理是什么 場(chang)效(xiao)應(ying)管的特點

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)(shi)“漏(lou)(lou)極(ji)(ji)(ji)(ji)-源(yuan)極(ji)(ji)(ji)(ji)間(jian)(jian)流(liu)(liu)經(jing)溝(gou)道(dao)(dao)的(de)(de)(de)(de)ID，用以(yi)柵極(ji)(ji)(ji)(ji)與溝(gou)道(dao)(dao)間(jian)(jian)的(de)(de)(de)(de)pn結(jie)形(xing)成的(de)(de)(de)(de)反(fan)偏的(de)(de)(de)(de)柵極(ji)(ji)(ji)(ji)電(dian)壓控制(zhi)ID”。更正確地說，ID流(liu)(liu)經(jing)通(tong)路的(de)(de)(de)(de)寬度，即溝(gou)道(dao)(dao)截面積，它是(shi)(shi)由pn結(jie)反(fan)偏的(de)(de)(de)(de)變(bian)化(hua)，產生耗盡層(ceng)擴展變(bian)化(hua)控制(zhi)的(de)(de)(de)(de)緣故。在VGS=0的(de)(de)(de)(de)非飽和區域，表示(shi)的(de)(de)(de)(de)過渡層(ceng)的(de)(de)(de)(de)擴展因為不很大，根據漏(lou)(lou)極(ji)(ji)(ji)(ji)-源(yuan)極(ji)(ji)(ji)(ji)間(jian)(jian)所(suo)加(jia)VDS的(de)(de)(de)(de)電(dian)場，源(yuan)極(ji)(ji)(ji)(ji)區域的(de)(de)(de)(de)某些電(dian)子被(bei)漏(lou)(lou)極(ji)(ji)(ji)(ji)拉(la)去，即從漏(lou)(lou)極(ji)(ji)(ji)(ji)向源(yuan)極(ji)(ji)(ji)(ji)有電(dian)流(liu)(liu)ID流(liu)(liu)動。從門極(ji)(ji)(ji)(ji)向漏(lou)(lou)極(ji)(ji)(ji)(ji)擴展的(de)(de)(de)(de)過度層(ceng)將溝(gou)道(dao)(dao)的(de)(de)(de)(de)一部分(fen)構成堵塞型，ID飽和。將這種(zhong)狀態稱為夾(jia)斷(duan)。這意味著(zhu)過渡層(ceng)將溝(gou)道(dao)(dao)的(de)(de)(de)(de)一部分(fen)阻(zu)擋，并不是(shi)(shi)電(dian)流(liu)(liu)被(bei)切斷(duan)。

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在(zai)過(guo)(guo)渡(du)(du)層(ceng)由于(yu)沒有(you)電(dian)(dian)(dian)(dian)子(zi)、空(kong)穴(xue)的(de)自由移(yi)(yi)動(dong)，在(zai)理想(xiang)狀態(tai)下幾乎(hu)具(ju)有(you)絕緣特性，通(tong)常(chang)電(dian)(dian)(dian)(dian)流(liu)也難(nan)流(liu)動(dong)。但是此時漏(lou)極(ji)-源(yuan)極(ji)間(jian)的(de)電(dian)(dian)(dian)(dian)場(chang)，實際上是兩(liang)個過(guo)(guo)渡(du)(du)層(ceng)接觸漏(lou)極(ji)與(yu)門極(ji)下部(bu)附近(jin)，由于(yu)漂(piao)(piao)移(yi)(yi)電(dian)(dian)(dian)(dian)場(chang)拉去(qu)的(de)高(gao)速電(dian)(dian)(dian)(dian)子(zi)通(tong)過(guo)(guo)過(guo)(guo)渡(du)(du)層(ceng)。因漂(piao)(piao)移(yi)(yi)電(dian)(dian)(dian)(dian)場(chang)的(de)強度幾乎(hu)不變產生(sheng)ID的(de)飽(bao)和現象。其次，VGS向負的(de)方向變化，讓(rang)VGS=VGS(off)，此時過(guo)(guo)渡(du)(du)層(ceng)大致(zhi)成為覆蓋(gai)全區域的(de)狀態(tai)。而且VDS的(de)電(dian)(dian)(dian)(dian)場(chang)大部(bu)分(fen)加(jia)到(dao)過(guo)(guo)渡(du)(du)層(ceng)上，將電(dian)(dian)(dian)(dian)子(zi)拉向漂(piao)(piao)移(yi)(yi)方向的(de)電(dian)(dian)(dian)(dian)場(chang)，只有(you)靠(kao)近(jin)源(yuan)極(ji)的(de)很短部(bu)分(fen)，這更(geng)使(shi)電(dian)(dian)(dian)(dian)流(liu)不能(neng)流(liu)通(tong)。

MOS場效應管電源開關電路

MOS場效應管也(ye)被(bei)稱(cheng)(cheng)為(wei)金屬氧化物(wu)半(ban)導體場(chang)(chang)效(xiao)應(ying)(ying)管(guan)(guan)(MetalOxideSemiconductor FieldEffect Transistor, MOSFET)。它一般(ban)有耗(hao)盡型(xing)(xing)(xing)和增(zeng)強(qiang)(qiang)型(xing)(xing)(xing)兩(liang)種。增(zeng)強(qiang)(qiang)型(xing)(xing)(xing)MOS場(chang)(chang)效(xiao)應(ying)(ying)管(guan)(guan)可分為(wei)NPN型(xing)(xing)(xing)PNP型(xing)(xing)(xing)。NPN型(xing)(xing)(xing)通常稱(cheng)(cheng)為(wei)N溝(gou)(gou)(gou)道(dao)型(xing)(xing)(xing)，PNP型(xing)(xing)(xing)也(ye)叫(jiao)P溝(gou)(gou)(gou)道(dao)型(xing)(xing)(xing)。對(dui)于(yu)N溝(gou)(gou)(gou)道(dao)的場(chang)(chang)效(xiao)應(ying)(ying)管(guan)(guan)其源(yuan)(yuan)極和漏(lou)極接在(zai)N型(xing)(xing)(xing)半(ban)導體上，同樣對(dui)于(yu)P溝(gou)(gou)(gou)道(dao)的場(chang)(chang)效(xiao)應(ying)(ying)管(guan)(guan)其源(yuan)(yuan)極和漏(lou)極則接在(zai)P型(xing)(xing)(xing)半(ban)導體上。場(chang)(chang)效(xiao)應(ying)(ying)管(guan)(guan)的輸(shu)(shu)出電(dian)流(liu)是由輸(shu)(shu)入(ru)的電(dian)壓（或稱(cheng)(cheng)電(dian)場(chang)(chang)）控(kong)制，可以認(ren)為(wei)輸(shu)(shu)入(ru)電(dian)流(liu)極小或沒有輸(shu)(shu)入(ru)電(dian)流(liu)，這使得(de)該器件有很高的輸(shu)(shu)入(ru)阻抗，同時(shi)這也(ye)是我(wo)們稱(cheng)(cheng)之為(wei)場(chang)(chang)效(xiao)應(ying)(ying)管(guan)(guan)的原因。

在(zai)(zai)(zai)(zai)二極(ji)(ji)(ji)(ji)管(guan)(guan)加上(shang)正(zheng)向電(dian)(dian)(dian)(dian)壓(ya)（P端(duan)(duan)(duan)(duan)接正(zheng)極(ji)(ji)(ji)(ji)，N端(duan)(duan)(duan)(duan)接負(fu)極(ji)(ji)(ji)(ji)）時(shi)，二極(ji)(ji)(ji)(ji)管(guan)(guan)導(dao)(dao)(dao)(dao)(dao)(dao)通，其PN結有電(dian)(dian)(dian)(dian)流(liu)通過(guo)。這是因為(wei)(wei)在(zai)(zai)(zai)(zai)P型(xing)(xing)(xing)半導(dao)(dao)(dao)(dao)(dao)(dao)體(ti)(ti)(ti)端(duan)(duan)(duan)(duan)為(wei)(wei)正(zheng)電(dian)(dian)(dian)(dian)壓(ya)時(shi)，N型(xing)(xing)(xing)半導(dao)(dao)(dao)(dao)(dao)(dao)體(ti)(ti)(ti)內(nei)的(de)(de)(de)(de)(de)(de)負(fu)電(dian)(dian)(dian)(dian)子被(bei)吸引(yin)而涌向加有正(zheng)電(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)(de)(de)(de)P型(xing)(xing)(xing)半導(dao)(dao)(dao)(dao)(dao)(dao)體(ti)(ti)(ti)端(duan)(duan)(duan)(duan)，而P型(xing)(xing)(xing)半導(dao)(dao)(dao)(dao)(dao)(dao)體(ti)(ti)(ti)端(duan)(duan)(duan)(duan)內(nei)的(de)(de)(de)(de)(de)(de)正(zheng)電(dian)(dian)(dian)(dian)子則朝N型(xing)(xing)(xing)半導(dao)(dao)(dao)(dao)(dao)(dao)體(ti)(ti)(ti)端(duan)(duan)(duan)(duan)運動，從(cong)而形成導(dao)(dao)(dao)(dao)(dao)(dao)通電(dian)(dian)(dian)(dian)流(liu)。同理，當(dang)二極(ji)(ji)(ji)(ji)管(guan)(guan)加上(shang)反向電(dian)(dian)(dian)(dian)壓(ya)（P端(duan)(duan)(duan)(duan)接負(fu)極(ji)(ji)(ji)(ji)，N端(duan)(duan)(duan)(duan)接正(zheng)極(ji)(ji)(ji)(ji)）時(shi)，這時(shi)在(zai)(zai)(zai)(zai)P型(xing)(xing)(xing)半導(dao)(dao)(dao)(dao)(dao)(dao)體(ti)(ti)(ti)端(duan)(duan)(duan)(duan)為(wei)(wei)負(fu)電(dian)(dian)(dian)(dian)壓(ya)，正(zheng)電(dian)(dian)(dian)(dian)子被(bei)聚(ju)集在(zai)(zai)(zai)(zai)P型(xing)(xing)(xing)半導(dao)(dao)(dao)(dao)(dao)(dao)體(ti)(ti)(ti)端(duan)(duan)(duan)(duan)，負(fu)電(dian)(dian)(dian)(dian)子則聚(ju)集在(zai)(zai)(zai)(zai)N型(xing)(xing)(xing)半導(dao)(dao)(dao)(dao)(dao)(dao)體(ti)(ti)(ti)端(duan)(duan)(duan)(duan)，電(dian)(dian)(dian)(dian)子不(bu)移動，其PN結沒有電(dian)(dian)(dian)(dian)流(liu)通過(guo)，二極(ji)(ji)(ji)(ji)管(guan)(guan)截止(zhi)(zhi)。在(zai)(zai)(zai)(zai)柵(zha)極(ji)(ji)(ji)(ji)沒有電(dian)(dian)(dian)(dian)壓(ya)時(shi)，由前(qian)面分(fen)析(xi)可知，在(zai)(zai)(zai)(zai)源(yuan)極(ji)(ji)(ji)(ji)與漏(lou)極(ji)(ji)(ji)(ji)之間(jian)(jian)(jian)不(bu)會有電(dian)(dian)(dian)(dian)流(liu)流(liu)過(guo)，此(ci)時(shi)場效應管(guan)(guan)處(chu)與截止(zhi)(zhi)狀態（圖7a）。當(dang)有一個正(zheng)電(dian)(dian)(dian)(dian)壓(ya)加在(zai)(zai)(zai)(zai)N溝(gou)道的(de)(de)(de)(de)(de)(de)MOS場效應管(guan)(guan)柵(zha)極(ji)(ji)(ji)(ji)上(shang)時(shi)，由于(yu)(yu)電(dian)(dian)(dian)(dian)場的(de)(de)(de)(de)(de)(de)作用(yong)，此(ci)時(shi)N型(xing)(xing)(xing)半導(dao)(dao)(dao)(dao)(dao)(dao)體(ti)(ti)(ti)的(de)(de)(de)(de)(de)(de)源(yuan)極(ji)(ji)(ji)(ji)和(he)漏(lou)極(ji)(ji)(ji)(ji)的(de)(de)(de)(de)(de)(de)負(fu)電(dian)(dian)(dian)(dian)子被(bei)吸引(yin)出來而涌向柵(zha)極(ji)(ji)(ji)(ji)，但由于(yu)(yu)氧化(hua)膜的(de)(de)(de)(de)(de)(de)阻擋，使得電(dian)(dian)(dian)(dian)子聚(ju)集在(zai)(zai)(zai)(zai)兩(liang)個N溝(gou)道之間(jian)(jian)(jian)的(de)(de)(de)(de)(de)(de)P型(xing)(xing)(xing)半導(dao)(dao)(dao)(dao)(dao)(dao)體(ti)(ti)(ti)中(zhong)（見(jian)圖7b），從(cong)而形成電(dian)(dian)(dian)(dian)流(liu)，使源(yuan)極(ji)(ji)(ji)(ji)和(he)漏(lou)極(ji)(ji)(ji)(ji)之間(jian)(jian)(jian)導(dao)(dao)(dao)(dao)(dao)(dao)通。可以想(xiang)像(xiang)為(wei)(wei)兩(liang)個N型(xing)(xing)(xing)半導(dao)(dao)(dao)(dao)(dao)(dao)體(ti)(ti)(ti)之間(jian)(jian)(jian)為(wei)(wei)一條(tiao)溝(gou)，柵(zha)極(ji)(ji)(ji)(ji)電(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)(de)(de)(de)建立相當(dang)于(yu)(yu)為(wei)(wei)它們(men)之間(jian)(jian)(jian)搭了一座(zuo)橋(qiao)(qiao)梁(liang)，該橋(qiao)(qiao)的(de)(de)(de)(de)(de)(de)大小由柵(zha)壓(ya)的(de)(de)(de)(de)(de)(de)大小決定(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(zu)合(he)在(zai)一起使用。當輸(shu)(shu)(shu)(shu)入(ru)端為(wei)低電(dian)(dian)平時，P溝道MOS場效(xiao)(xiao)應管(guan)(guan)導通(tong)(tong)(tong)(tong)，輸(shu)(shu)(shu)(shu)出端與電(dian)(dian)源(yuan)正極(ji)(ji)接通(tong)(tong)(tong)(tong)。當輸(shu)(shu)(shu)(shu)入(ru)端為(wei)高電(dian)(dian)平時，N溝道MOS場效(xiao)(xiao)應管(guan)(guan)導通(tong)(tong)(tong)(tong)，輸(shu)(shu)(shu)(shu)出端與電(dian)(dian)源(yuan)地接通(tong)(tong)(tong)(tong)。在(zai)該(gai)電(dian)(dian)路(lu)中(zhong)，P溝道MOS場效(xiao)(xiao)應管(guan)(guan)和(he)N溝道MOS場效(xiao)(xiao)應管(guan)(guan)總是在(zai)相(xiang)反(fan)的狀態下工作，其相(xiang)位輸(shu)(shu)(shu)(shu)入(ru)端和(he)輸(shu)(shu)(shu)(shu)出端相(xiang)反(fan)。通(tong)(tong)(tong)(tong)過這種工作方式我們可以獲得較大(da)的電(dian)(dian)流輸(shu)(shu)(shu)(shu)出。同(tong)時由于漏電(dian)(dian)流的影(ying)響，使得柵(zha)壓在(zai)還沒(mei)有到(dao)(dao)0V，通(tong)(tong)(tong)(tong)常在(zai)柵(zha)極(ji)(ji)電(dian)(dian)壓小(xiao)于1到(dao)(dao)2V時，MOS場效(xiao)(xiao)應管(guan)(guan)既被(bei)關斷。不(bu)(bu)同(tong)場效(xiao)(xiao)應管(guan)(guan)其關斷電(dian)(dian)壓略有不(bu)(bu)同(tong)。也(ye)正因為(wei)如此(ci)，使得該(gai)電(dian)(dian)路(lu)不(bu)(bu)會因為(wei)兩管(guan)(guan)同(tong)時導通(tong)(tong)(tong)(tong)而造成(cheng)電(dian)(dian)源(yuan)短路(lu)。

場效應管的特點

（1）場效應管(guan)是電(dian)壓控(kong)制器件，它通過VGS(柵源電(dian)壓)來控(kong)制ID（漏極電(dian)流(liu)）；

（2）場效(xiao)應管的控制輸入端(duan)電流極小，因(yin)此(ci)它(ta)的輸入電阻（107～1012Ω）很大。

（3）它(ta)是利用(yong)多數載(zai)流子導電(dian)，因(yin)此它(ta)的溫度穩定性較好；

（4）它組成(cheng)的放(fang)大電(dian)路(lu)的電(dian)壓(ya)放(fang)大系數要小于三(san)極管組成(cheng)放(fang)大電(dian)路(lu)的電(dian)壓(ya)放(fang)大系數；

（5）場(chang)效應(ying)管的抗輻射能力強；

（6）由于它不存在(zai)雜亂運動的電子擴散引(yin)起的散粒(li)噪(zao)聲，所以噪(zao)聲低。