【場(chang)(chang)效(xiao)應管工作原理】場(chang)(chang)效(xiao)應管的工作原理是什么(me) 場(chang)(chang)效(xiao)應管的特(te)點

場效應管的工作原理是什么

場效應管工(gong)作原理用(yong)一句話說(shuo)，就是“漏極(ji)(ji)(ji)-源極(ji)(ji)(ji)間(jian)(jian)流經(jing)溝(gou)(gou)道的(de)(de)(de)(de)(de)(de)ID，用(yong)以柵(zha)極(ji)(ji)(ji)與溝(gou)(gou)道間(jian)(jian)的(de)(de)(de)(de)(de)(de)pn結(jie)形成(cheng)(cheng)的(de)(de)(de)(de)(de)(de)反偏(pian)的(de)(de)(de)(de)(de)(de)柵(zha)極(ji)(ji)(ji)電(dian)壓控制ID”。更正(zheng)確地(di)說(shuo)，ID流經(jing)通路的(de)(de)(de)(de)(de)(de)寬度，即(ji)溝(gou)(gou)道截面積，它是由pn結(jie)反偏(pian)的(de)(de)(de)(de)(de)(de)變(bian)化，產(chan)生耗盡層擴(kuo)(kuo)展變(bian)化控制的(de)(de)(de)(de)(de)(de)緣故。在VGS=0的(de)(de)(de)(de)(de)(de)非飽(bao)和(he)區域，表示的(de)(de)(de)(de)(de)(de)過渡層的(de)(de)(de)(de)(de)(de)擴(kuo)(kuo)展因為不很大(da)，根據漏極(ji)(ji)(ji)-源極(ji)(ji)(ji)間(jian)(jian)所加(jia)VDS的(de)(de)(de)(de)(de)(de)電(dian)場，源極(ji)(ji)(ji)區域的(de)(de)(de)(de)(de)(de)某些電(dian)子(zi)被漏極(ji)(ji)(ji)拉(la)去，即(ji)從漏極(ji)(ji)(ji)向源極(ji)(ji)(ji)有電(dian)流ID流動。從門極(ji)(ji)(ji)向漏極(ji)(ji)(ji)擴(kuo)(kuo)展的(de)(de)(de)(de)(de)(de)過度層將(jiang)溝(gou)(gou)道的(de)(de)(de)(de)(de)(de)一部(bu)分構成(cheng)(cheng)堵塞型(xing)，ID飽(bao)和(he)。將(jiang)這(zhe)種狀態稱為夾斷。這(zhe)意味著過渡層將(jiang)溝(gou)(gou)道的(de)(de)(de)(de)(de)(de)一部(bu)分阻擋(dang)，并(bing)不是電(dian)流被切斷。

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在(zai)過(guo)(guo)(guo)渡(du)層(ceng)由(you)于(yu)(yu)沒有電(dian)子(zi)、空穴的(de)(de)自由(you)移(yi)動，在(zai)理想狀(zhuang)態下(xia)幾(ji)乎具(ju)有絕(jue)緣特性，通(tong)(tong)(tong)常電(dian)流(liu)也難流(liu)動。但(dan)是(shi)(shi)此時漏極(ji)(ji)-源極(ji)(ji)間的(de)(de)電(dian)場(chang)，實際上是(shi)(shi)兩個(ge)過(guo)(guo)(guo)渡(du)層(ceng)接觸漏極(ji)(ji)與(yu)門極(ji)(ji)下(xia)部附近(jin)，由(you)于(yu)(yu)漂(piao)移(yi)電(dian)場(chang)拉(la)去的(de)(de)高速電(dian)子(zi)通(tong)(tong)(tong)過(guo)(guo)(guo)過(guo)(guo)(guo)渡(du)層(ceng)。因漂(piao)移(yi)電(dian)場(chang)的(de)(de)強度幾(ji)乎不(bu)變產生ID的(de)(de)飽和現象(xiang)。其(qi)次(ci)，VGS向負(fu)的(de)(de)方(fang)向變化，讓VGS=VGS(off)，此時過(guo)(guo)(guo)渡(du)層(ceng)大致成為覆蓋全區域的(de)(de)狀(zhuang)態。而(er)且VDS的(de)(de)電(dian)場(chang)大部分加到(dao)過(guo)(guo)(guo)渡(du)層(ceng)上，將電(dian)子(zi)拉(la)向漂(piao)移(yi)方(fang)向的(de)(de)電(dian)場(chang)，只有靠近(jin)源極(ji)(ji)的(de)(de)很短部分，這更使電(dian)流(liu)不(bu)能流(liu)通(tong)(tong)(tong)。

MOS場效應管電源開關電路

MOS場效應管也被稱為(wei)(wei)(wei)金屬氧化(hua)物半(ban)導(dao)體(ti)場(chang)效(xiao)應(ying)管(MetalOxideSemiconductor FieldEffect Transistor, MOSFET)。它一般有耗盡型和增強(qiang)型兩(liang)種。增強(qiang)型MOS場(chang)效(xiao)應(ying)管可分為(wei)(wei)(wei)NPN型PNP型。NPN型通常稱為(wei)(wei)(wei)N溝(gou)道型，PNP型也叫P溝(gou)道型。對(dui)于(yu)N溝(gou)道的(de)(de)場(chang)效(xiao)應(ying)管其源(yuan)極和漏極接(jie)(jie)在(zai)N型半(ban)導(dao)體(ti)上，同(tong)樣對(dui)于(yu)P溝(gou)道的(de)(de)場(chang)效(xiao)應(ying)管其源(yuan)極和漏極則(ze)接(jie)(jie)在(zai)P型半(ban)導(dao)體(ti)上。場(chang)效(xiao)應(ying)管的(de)(de)輸(shu)(shu)出電(dian)(dian)(dian)流是由輸(shu)(shu)入的(de)(de)電(dian)(dian)(dian)壓（或(huo)(huo)稱電(dian)(dian)(dian)場(chang)）控(kong)制，可以認(ren)為(wei)(wei)(wei)輸(shu)(shu)入電(dian)(dian)(dian)流極小或(huo)(huo)沒(mei)有輸(shu)(shu)入電(dian)(dian)(dian)流，這使得該器(qi)件有很(hen)高的(de)(de)輸(shu)(shu)入阻抗，同(tong)時這也是我們(men)稱之為(wei)(wei)(wei)場(chang)效(xiao)應(ying)管的(de)(de)原因。

在(zai)二極(ji)(ji)(ji)(ji)(ji)(ji)管(guan)加上(shang)正(zheng)(zheng)向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)（P端(duan)(duan)接(jie)正(zheng)(zheng)極(ji)(ji)(ji)(ji)(ji)(ji)，N端(duan)(duan)接(jie)負(fu)極(ji)(ji)(ji)(ji)(ji)(ji)）時，二極(ji)(ji)(ji)(ji)(ji)(ji)管(guan)導(dao)(dao)(dao)通，其(qi)(qi)PN結有電(dian)(dian)(dian)(dian)流通過。這(zhe)是因為(wei)在(zai)P型(xing)(xing)半(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)為(wei)正(zheng)(zheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)時，N型(xing)(xing)半(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)(ti)(ti)內的(de)負(fu)電(dian)(dian)(dian)(dian)子(zi)被吸(xi)(xi)引而涌(yong)向(xiang)加有正(zheng)(zheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)P型(xing)(xing)半(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)，而P型(xing)(xing)半(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)內的(de)正(zheng)(zheng)電(dian)(dian)(dian)(dian)子(zi)則(ze)朝(chao)N型(xing)(xing)半(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)運動(dong)，從(cong)而形(xing)成導(dao)(dao)(dao)通電(dian)(dian)(dian)(dian)流。同理，當二極(ji)(ji)(ji)(ji)(ji)(ji)管(guan)加上(shang)反向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)（P端(duan)(duan)接(jie)負(fu)極(ji)(ji)(ji)(ji)(ji)(ji)，N端(duan)(duan)接(jie)正(zheng)(zheng)極(ji)(ji)(ji)(ji)(ji)(ji)）時，這(zhe)時在(zai)P型(xing)(xing)半(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)為(wei)負(fu)電(dian)(dian)(dian)(dian)壓(ya)(ya)，正(zheng)(zheng)電(dian)(dian)(dian)(dian)子(zi)被聚集(ji)在(zai)P型(xing)(xing)半(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)，負(fu)電(dian)(dian)(dian)(dian)子(zi)則(ze)聚集(ji)在(zai)N型(xing)(xing)半(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)(ti)(ti)端(duan)(duan)，電(dian)(dian)(dian)(dian)子(zi)不移動(dong)，其(qi)(qi)PN結沒(mei)有電(dian)(dian)(dian)(dian)流通過，二極(ji)(ji)(ji)(ji)(ji)(ji)管(guan)截(jie)止。在(zai)柵(zha)(zha)(zha)極(ji)(ji)(ji)(ji)(ji)(ji)沒(mei)有電(dian)(dian)(dian)(dian)壓(ya)(ya)時，由前面分析(xi)可知，在(zai)源極(ji)(ji)(ji)(ji)(ji)(ji)與漏(lou)極(ji)(ji)(ji)(ji)(ji)(ji)之間不會有電(dian)(dian)(dian)(dian)流流過，此(ci)時場(chang)(chang)(chang)效應(ying)管(guan)處與截(jie)止狀態（圖7a）。當有一(yi)個正(zheng)(zheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)加在(zai)N溝(gou)道(dao)的(de)MOS場(chang)(chang)(chang)效應(ying)管(guan)柵(zha)(zha)(zha)極(ji)(ji)(ji)(ji)(ji)(ji)上(shang)時，由于(yu)(yu)電(dian)(dian)(dian)(dian)場(chang)(chang)(chang)的(de)作用，此(ci)時N型(xing)(xing)半(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)(ti)(ti)的(de)源極(ji)(ji)(ji)(ji)(ji)(ji)和(he)漏(lou)極(ji)(ji)(ji)(ji)(ji)(ji)的(de)負(fu)電(dian)(dian)(dian)(dian)子(zi)被吸(xi)(xi)引出(chu)來(lai)而涌(yong)向(xiang)柵(zha)(zha)(zha)極(ji)(ji)(ji)(ji)(ji)(ji)，但(dan)由于(yu)(yu)氧化膜的(de)阻擋，使得電(dian)(dian)(dian)(dian)子(zi)聚集(ji)在(zai)兩個N溝(gou)道(dao)之間的(de)P型(xing)(xing)半(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)(ti)(ti)中（見圖7b），從(cong)而形(xing)成電(dian)(dian)(dian)(dian)流，使源極(ji)(ji)(ji)(ji)(ji)(ji)和(he)漏(lou)極(ji)(ji)(ji)(ji)(ji)(ji)之間導(dao)(dao)(dao)通。可以想像為(wei)兩個N型(xing)(xing)半(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)(ti)(ti)之間為(wei)一(yi)條溝(gou)，柵(zha)(zha)(zha)極(ji)(ji)(ji)(ji)(ji)(ji)電(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)建立相當于(yu)(yu)為(wei)它們之間搭了一(yi)座橋梁，該橋的(de)大(da)小由柵(zha)(zha)(zha)壓(ya)(ya)的(de)大(da)小決定。

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(he)在(zai)一起使用。當輸入端為低(di)電(dian)(dian)(dian)平時，P溝道(dao)MOS場效(xiao)(xiao)(xiao)應(ying)(ying)管導通(tong)，輸出(chu)端與電(dian)(dian)(dian)源正極(ji)接通(tong)。當輸入端為高(gao)電(dian)(dian)(dian)平時，N溝道(dao)MOS場效(xiao)(xiao)(xiao)應(ying)(ying)管導通(tong)，輸出(chu)端與電(dian)(dian)(dian)源地接通(tong)。在(zai)該電(dian)(dian)(dian)路中，P溝道(dao)MOS場效(xiao)(xiao)(xiao)應(ying)(ying)管和N溝道(dao)MOS場效(xiao)(xiao)(xiao)應(ying)(ying)管總是在(zai)相反的狀態(tai)下工(gong)作(zuo)，其相位輸入端和輸出(chu)端相反。通(tong)過這種(zhong)工(gong)作(zuo)方式我們(men)可(ke)以獲得較大的電(dian)(dian)(dian)流(liu)輸出(chu)。同(tong)時由于(yu)漏電(dian)(dian)(dian)流(liu)的影響，使得柵壓在(zai)還沒有到0V，通(tong)常在(zai)柵極(ji)電(dian)(dian)(dian)壓小(xiao)于(yu)1到2V時，MOS場效(xiao)(xiao)(xiao)應(ying)(ying)管既被關斷。不(bu)(bu)同(tong)場效(xiao)(xiao)(xiao)應(ying)(ying)管其關斷電(dian)(dian)(dian)壓略有不(bu)(bu)同(tong)。也(ye)正因(yin)為如此，使得該電(dian)(dian)(dian)路不(bu)(bu)會(hui)因(yin)為兩(liang)管同(tong)時導通(tong)而造成電(dian)(dian)(dian)源短(duan)路。

場效應管的特點

（1）場效應管是電(dian)(dian)壓控制(zhi)器件(jian)，它通(tong)過VGS(柵(zha)源(yuan)電(dian)(dian)壓)來控制(zhi)ID（漏極電(dian)(dian)流(liu)）；

（2）場效應管的控(kong)制(zhi)輸(shu)入端(duan)電流極小，因(yin)此它的輸(shu)入電阻（107～1012Ω）很(hen)大。

（3）它是利用多數載流子導電，因此它的溫(wen)度(du)穩定性較好；

（4）它(ta)組(zu)成(cheng)的(de)放大電路的(de)電壓(ya)放大系(xi)數(shu)要小于三極管組(zu)成(cheng)放大電路的(de)電壓(ya)放大系(xi)數(shu)；

（5）場效應管(guan)的(de)抗輻射能(neng)力(li)強(qiang)；

（6）由(you)于(yu)它(ta)不存在雜亂(luan)運動的電子擴散引起(qi)的散粒噪聲，所以噪聲低。