【場(chang)效應(ying)管(guan)工作原(yuan)理(li)】場(chang)效應(ying)管(guan)的工作原(yuan)理(li)是什(shen)么 場(chang)效應(ying)管(guan)的特點

場效應管的工作原理是什么

場效應管工作(zuo)原(yuan)理(li)用一句(ju)話說，就是“漏(lou)極(ji)(ji)(ji)-源(yuan)極(ji)(ji)(ji)間流(liu)(liu)經溝道(dao)(dao)的(de)ID，用以柵極(ji)(ji)(ji)與溝道(dao)(dao)間的(de)pn結形成的(de)反(fan)偏(pian)的(de)柵極(ji)(ji)(ji)電(dian)壓控(kong)制(zhi)ID”。更正確地說，ID流(liu)(liu)經通(tong)路的(de)寬度，即(ji)溝道(dao)(dao)截(jie)面(mian)積，它(ta)是由pn結反(fan)偏(pian)的(de)變(bian)化(hua)，產生耗盡層(ceng)擴(kuo)展(zhan)(zhan)(zhan)變(bian)化(hua)控(kong)制(zhi)的(de)緣故。在VGS=0的(de)非飽和區域，表示(shi)的(de)過(guo)渡(du)層(ceng)的(de)擴(kuo)展(zhan)(zhan)(zhan)因為不很(hen)大，根據漏(lou)極(ji)(ji)(ji)-源(yuan)極(ji)(ji)(ji)間所(suo)加(jia)VDS的(de)電(dian)場，源(yuan)極(ji)(ji)(ji)區域的(de)某些電(dian)子被漏(lou)極(ji)(ji)(ji)拉去，即(ji)從(cong)漏(lou)極(ji)(ji)(ji)向源(yuan)極(ji)(ji)(ji)有(you)電(dian)流(liu)(liu)ID流(liu)(liu)動。從(cong)門極(ji)(ji)(ji)向漏(lou)極(ji)(ji)(ji)擴(kuo)展(zhan)(zhan)(zhan)的(de)過(guo)度層(ceng)將溝道(dao)(dao)的(de)一部分構成堵塞(sai)型，ID飽和。將這(zhe)種狀(zhuang)態稱為夾斷。這(zhe)意(yi)味著過(guo)渡(du)層(ceng)將溝道(dao)(dao)的(de)一部分阻(zu)擋，并(bing)不是電(dian)流(liu)(liu)被切斷。

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在過(guo)渡(du)(du)(du)層(ceng)由(you)于(yu)沒有(you)電(dian)(dian)(dian)(dian)子、空穴的(de)(de)自由(you)移動，在理想(xiang)狀態(tai)下(xia)幾乎具有(you)絕緣(yuan)特性，通常電(dian)(dian)(dian)(dian)流也難(nan)流動。但是(shi)此時漏極(ji)(ji)-源極(ji)(ji)間的(de)(de)電(dian)(dian)(dian)(dian)場，實際(ji)上是(shi)兩個(ge)過(guo)渡(du)(du)(du)層(ceng)接觸漏極(ji)(ji)與(yu)門(men)極(ji)(ji)下(xia)部附近，由(you)于(yu)漂(piao)(piao)移電(dian)(dian)(dian)(dian)場拉去的(de)(de)高(gao)速電(dian)(dian)(dian)(dian)子通過(guo)過(guo)渡(du)(du)(du)層(ceng)。因漂(piao)(piao)移電(dian)(dian)(dian)(dian)場的(de)(de)強度幾乎不變產生ID的(de)(de)飽和現象。其次，VGS向(xiang)負的(de)(de)方(fang)向(xiang)變化，讓(rang)VGS=VGS(off)，此時過(guo)渡(du)(du)(du)層(ceng)大(da)致成為(wei)覆(fu)蓋全區域的(de)(de)狀態(tai)。而且VDS的(de)(de)電(dian)(dian)(dian)(dian)場大(da)部分加到過(guo)渡(du)(du)(du)層(ceng)上，將電(dian)(dian)(dian)(dian)子拉向(xiang)漂(piao)(piao)移方(fang)向(xiang)的(de)(de)電(dian)(dian)(dian)(dian)場，只有(you)靠近源極(ji)(ji)的(de)(de)很(hen)短部分，這(zhe)更(geng)使電(dian)(dian)(dian)(dian)流不能流通。

MOS場效應管電源開關電路

MOS場效應管也被稱(cheng)(cheng)(cheng)為(wei)(wei)金屬氧化物半(ban)導(dao)體(ti)場(chang)效應(ying)(ying)管(guan)(MetalOxideSemiconductor FieldEffect Transistor, MOSFET)。它一般(ban)有(you)耗盡(jin)型(xing)(xing)和增(zeng)強(qiang)型(xing)(xing)兩種。增(zeng)強(qiang)型(xing)(xing)MOS場(chang)效應(ying)(ying)管(guan)可分為(wei)(wei)NPN型(xing)(xing)PNP型(xing)(xing)。NPN型(xing)(xing)通常稱(cheng)(cheng)(cheng)為(wei)(wei)N溝(gou)(gou)道(dao)型(xing)(xing)，PNP型(xing)(xing)也叫P溝(gou)(gou)道(dao)型(xing)(xing)。對于(yu)N溝(gou)(gou)道(dao)的(de)場(chang)效應(ying)(ying)管(guan)其源(yuan)極(ji)(ji)和漏極(ji)(ji)接在(zai)N型(xing)(xing)半(ban)導(dao)體(ti)上，同樣對于(yu)P溝(gou)(gou)道(dao)的(de)場(chang)效應(ying)(ying)管(guan)其源(yuan)極(ji)(ji)和漏極(ji)(ji)則接在(zai)P型(xing)(xing)半(ban)導(dao)體(ti)上。場(chang)效應(ying)(ying)管(guan)的(de)輸(shu)出電流是由輸(shu)入的(de)電壓(ya)（或(huo)(huo)稱(cheng)(cheng)(cheng)電場(chang)）控制，可以(yi)認為(wei)(wei)輸(shu)入電流極(ji)(ji)小或(huo)(huo)沒(mei)有(you)輸(shu)入電流，這使得該器件(jian)有(you)很高的(de)輸(shu)入阻抗，同時這也是我們稱(cheng)(cheng)(cheng)之為(wei)(wei)場(chang)效應(ying)(ying)管(guan)的(de)原(yuan)因。

在(zai)(zai)二(er)極(ji)(ji)(ji)(ji)管(guan)加(jia)上正(zheng)(zheng)向電(dian)(dian)(dian)(dian)壓(ya)(ya)（P端(duan)(duan)(duan)接(jie)(jie)正(zheng)(zheng)極(ji)(ji)(ji)(ji)，N端(duan)(duan)(duan)接(jie)(jie)負極(ji)(ji)(ji)(ji)）時(shi)(shi)，二(er)極(ji)(ji)(ji)(ji)管(guan)導(dao)(dao)(dao)通(tong)(tong)，其PN結(jie)有(you)電(dian)(dian)(dian)(dian)流(liu)(liu)通(tong)(tong)過。這(zhe)是(shi)因為(wei)在(zai)(zai)P型(xing)半(ban)(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)端(duan)(duan)(duan)為(wei)正(zheng)(zheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)時(shi)(shi)，N型(xing)半(ban)(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)內(nei)的(de)(de)負電(dian)(dian)(dian)(dian)子(zi)被吸引而(er)(er)涌(yong)向加(jia)有(you)正(zheng)(zheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)P型(xing)半(ban)(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)端(duan)(duan)(duan)，而(er)(er)P型(xing)半(ban)(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)端(duan)(duan)(duan)內(nei)的(de)(de)正(zheng)(zheng)電(dian)(dian)(dian)(dian)子(zi)則朝N型(xing)半(ban)(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)端(duan)(duan)(duan)運動(dong)，從(cong)而(er)(er)形成導(dao)(dao)(dao)通(tong)(tong)電(dian)(dian)(dian)(dian)流(liu)(liu)。同理，當二(er)極(ji)(ji)(ji)(ji)管(guan)加(jia)上反向電(dian)(dian)(dian)(dian)壓(ya)(ya)（P端(duan)(duan)(duan)接(jie)(jie)負極(ji)(ji)(ji)(ji)，N端(duan)(duan)(duan)接(jie)(jie)正(zheng)(zheng)極(ji)(ji)(ji)(ji)）時(shi)(shi)，這(zhe)時(shi)(shi)在(zai)(zai)P型(xing)半(ban)(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)端(duan)(duan)(duan)為(wei)負電(dian)(dian)(dian)(dian)壓(ya)(ya)，正(zheng)(zheng)電(dian)(dian)(dian)(dian)子(zi)被聚集在(zai)(zai)P型(xing)半(ban)(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)端(duan)(duan)(duan)，負電(dian)(dian)(dian)(dian)子(zi)則聚集在(zai)(zai)N型(xing)半(ban)(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)端(duan)(duan)(duan)，電(dian)(dian)(dian)(dian)子(zi)不移動(dong)，其PN結(jie)沒有(you)電(dian)(dian)(dian)(dian)流(liu)(liu)通(tong)(tong)過，二(er)極(ji)(ji)(ji)(ji)管(guan)截止。在(zai)(zai)柵(zha)(zha)極(ji)(ji)(ji)(ji)沒有(you)電(dian)(dian)(dian)(dian)壓(ya)(ya)時(shi)(shi)，由(you)前面分(fen)析可知(zhi)，在(zai)(zai)源(yuan)(yuan)極(ji)(ji)(ji)(ji)與漏極(ji)(ji)(ji)(ji)之間不會有(you)電(dian)(dian)(dian)(dian)流(liu)(liu)流(liu)(liu)過，此時(shi)(shi)場效(xiao)應管(guan)處(chu)與截止狀態（圖7a）。當有(you)一個正(zheng)(zheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)加(jia)在(zai)(zai)N溝道(dao)的(de)(de)MOS場效(xiao)應管(guan)柵(zha)(zha)極(ji)(ji)(ji)(ji)上時(shi)(shi)，由(you)于電(dian)(dian)(dian)(dian)場的(de)(de)作用，此時(shi)(shi)N型(xing)半(ban)(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)的(de)(de)源(yuan)(yuan)極(ji)(ji)(ji)(ji)和漏極(ji)(ji)(ji)(ji)的(de)(de)負電(dian)(dian)(dian)(dian)子(zi)被吸引出來而(er)(er)涌(yong)向柵(zha)(zha)極(ji)(ji)(ji)(ji)，但(dan)由(you)于氧化膜(mo)的(de)(de)阻擋，使得電(dian)(dian)(dian)(dian)子(zi)聚集在(zai)(zai)兩(liang)(liang)個N溝道(dao)之間的(de)(de)P型(xing)半(ban)(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)中(zhong)（見圖7b），從(cong)而(er)(er)形成電(dian)(dian)(dian)(dian)流(liu)(liu)，使源(yuan)(yuan)極(ji)(ji)(ji)(ji)和漏極(ji)(ji)(ji)(ji)之間導(dao)(dao)(dao)通(tong)(tong)。可以(yi)想像為(wei)兩(liang)(liang)個N型(xing)半(ban)(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)(ti)之間為(wei)一條(tiao)溝，柵(zha)(zha)極(ji)(ji)(ji)(ji)電(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)建(jian)立相當于為(wei)它們之間搭了(le)一座(zuo)橋(qiao)梁(liang)，該橋(qiao)的(de)(de)大小由(you)柵(zha)(zha)壓(ya)(ya)的(de)(de)大小決(jue)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(zu)合在(zai)(zai)(zai)一起使(shi)用。當(dang)(dang)輸入端(duan)為低電(dian)(dian)(dian)平時(shi)，P溝(gou)(gou)道(dao)MOS場(chang)效應管(guan)導(dao)通(tong)，輸出(chu)端(duan)與電(dian)(dian)(dian)源(yuan)(yuan)正極接通(tong)。當(dang)(dang)輸入端(duan)為高(gao)電(dian)(dian)(dian)平時(shi)，N溝(gou)(gou)道(dao)MOS場(chang)效應管(guan)導(dao)通(tong)，輸出(chu)端(duan)與電(dian)(dian)(dian)源(yuan)(yuan)地接通(tong)。在(zai)(zai)(zai)該(gai)電(dian)(dian)(dian)路(lu)中，P溝(gou)(gou)道(dao)MOS場(chang)效應管(guan)和N溝(gou)(gou)道(dao)MOS場(chang)效應管(guan)總(zong)是在(zai)(zai)(zai)相(xiang)反的狀態(tai)下(xia)工作，其相(xiang)位輸入端(duan)和輸出(chu)端(duan)相(xiang)反。通(tong)過(guo)這種工作方式我們可以獲得較大(da)的電(dian)(dian)(dian)流輸出(chu)。同(tong)(tong)時(shi)由于漏電(dian)(dian)(dian)流的影響(xiang)，使(shi)得柵(zha)壓在(zai)(zai)(zai)還沒有到0V，通(tong)常在(zai)(zai)(zai)柵(zha)極電(dian)(dian)(dian)壓小于1到2V時(shi)，MOS場(chang)效應管(guan)既(ji)被關斷(duan)。不同(tong)(tong)場(chang)效應管(guan)其關斷(duan)電(dian)(dian)(dian)壓略有不同(tong)(tong)。也(ye)正因為如此(ci)，使(shi)得該(gai)電(dian)(dian)(dian)路(lu)不會因為兩(liang)管(guan)同(tong)(tong)時(shi)導(dao)通(tong)而造成電(dian)(dian)(dian)源(yuan)(yuan)短路(lu)。

場效應管的特點

（1）場效應管是電壓控(kong)制(zhi)器(qi)件(jian)，它通過VGS(柵源電壓)來控(kong)制(zhi)ID（漏極(ji)電流(liu)）；

（2）場(chang)效應管(guan)的(de)控制輸(shu)入(ru)端電流極小，因(yin)此它的(de)輸(shu)入(ru)電阻（107～1012Ω）很大。

（3）它(ta)是利用多數載流子導電，因(yin)此(ci)它(ta)的溫度穩定性較好(hao)；

（4）它組(zu)成的(de)放大(da)(da)電(dian)路的(de)電(dian)壓放大(da)(da)系(xi)數(shu)(shu)要(yao)小于三極管組(zu)成放大(da)(da)電(dian)路的(de)電(dian)壓放大(da)(da)系(xi)數(shu)(shu)；

（5）場效應管的抗輻(fu)射(she)能力(li)強；

（6）由于它不存在雜亂運動的(de)電子擴(kuo)散引(yin)起的(de)散粒(li)噪聲(sheng)，所(suo)以噪聲(sheng)低。