晶(jing)體二極(ji)管(guan)為一(yi)個由(you)(you)p型半導體和n型半導體形(xing)成的(de)(de)(de)(de)pn結，在其界(jie)面處兩側形(xing)成空間(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)層，并建(jian)有自建(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)(chang)。當不存在外(wai)(wai)加(jia)(jia)(jia)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓時(shi)(shi)，由(you)(you)于pn結兩邊載(zai)流(liu)子濃度(du)差引(yin)起的(de)(de)(de)(de)擴(kuo)散(san)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)和自建(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)(chang)引(yin)起的(de)(de)(de)(de)漂移電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)相等(deng)而處于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平衡狀態。當外(wai)(wai)界(jie)有正向(xiang)(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓偏(pian)(pian)置(zhi)(zhi)時(shi)(shi)，外(wai)(wai)界(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)(chang)和自建(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)(chang)的(de)(de)(de)(de)互相抑消(xiao)作(zuo)用使載(zai)流(liu)子的(de)(de)(de)(de)擴(kuo)散(san)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)增加(jia)(jia)(jia)引(yin)起了正向(xiang)(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。當外(wai)(wai)界(jie)有反向(xiang)(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓偏(pian)(pian)置(zhi)(zhi)時(shi)(shi)，外(wai)(wai)界(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)(chang)和自建(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)(chang)進一(yi)步加(jia)(jia)(jia)強，形(xing)成在一(yi)定(ding)反向(xiang)(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓范(fan)圍(wei)內與反向(xiang)(xiang)偏(pian)(pian)置(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓值無關的(de)(de)(de)(de)反向(xiang)(xiang)飽和電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)I0。當外(wai)(wai)加(jia)(jia)(jia)的(de)(de)(de)(de)反向(xiang)(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓高到一(yi)定(ding)程度(du)時(shi)(shi)，pn結空間(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)層中(zhong)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)(chang)強度(du)達到臨界(jie)值產生載(zai)流(liu)子的(de)(de)(de)(de)倍增過程，產生大量(liang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子空穴(xue)對，產生了數(shu)值很大的(de)(de)(de)(de)反向(xiang)(xiang)擊(ji)穿(chuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，稱(cheng)為二極(ji)管(guan)的(de)(de)(de)(de)擊(ji)穿(chuan)現象。pn結的(de)(de)(de)(de)反向(xiang)(xiang)擊(ji)穿(chuan)有齊(qi)納(na)擊(ji)穿(chuan)和雪崩擊(ji)穿(chuan)之(zhi)分。

　　二極管的特性

　　正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)性：二(er)(er)極(ji)管(guan)(guan)外加正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)壓(ya)(ya)(ya)(ya)時，在正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)特性的(de)(de)(de)起(qi)始部(bu)分，正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)壓(ya)(ya)(ya)(ya)很小，不(bu)足以克(ke)服(fu)PN結(jie)內電(dian)場(chang)的(de)(de)(de)阻擋作用(yong)，正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)流(liu)幾乎(hu)為(wei)零，這(zhe)一(yi)段稱為(wei)死(si)區。這(zhe)個不(bu)能使(shi)二(er)(er)極(ji)管(guan)(guan)導(dao)(dao)通(tong)的(de)(de)(de)正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)壓(ya)(ya)(ya)(ya)稱為(wei)死(si)區電(dian)壓(ya)(ya)(ya)(ya)。當(dang)正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)壓(ya)(ya)(ya)(ya)大于死(si)區電(dian)壓(ya)(ya)(ya)(ya)以后，PN結(jie)內電(dian)場(chang)被克(ke)服(fu)，二(er)(er)極(ji)管(guan)(guan)正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)導(dao)(dao)通(tong)，電(dian)流(liu)隨電(dian)壓(ya)(ya)(ya)(ya)增大而迅速上升。在正(zheng)(zheng)(zheng)(zheng)(zheng)常使(shi)用(yong)的(de)(de)(de)電(dian)流(liu)范(fan)圍內，導(dao)(dao)通(tong)時二(er)(er)極(ji)管(guan)(guan)的(de)(de)(de)端(duan)電(dian)壓(ya)(ya)(ya)(ya)幾乎(hu)維持(chi)不(bu)變，這(zhe)個電(dian)壓(ya)(ya)(ya)(ya)稱為(wei)二(er)(er)極(ji)管(guan)(guan)的(de)(de)(de)正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)壓(ya)(ya)(ya)(ya)。當(dang)二(er)(er)極(ji)管(guan)(guan)兩端(duan)的(de)(de)(de)正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)壓(ya)(ya)(ya)(ya)超過一(yi)定數值(zhi)，內電(dian)場(chang)很快(kuai)被削弱，特性電(dian)流(liu)迅速增長，二(er)(er)極(ji)管(guan)(guan)正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)導(dao)(dao)通(tong)。叫做門坎電(dian)壓(ya)(ya)(ya)(ya)或(huo)閾值(zhi)電(dian)壓(ya)(ya)(ya)(ya)，硅管(guan)(guan)約(yue)為(wei)0.5V，鍺管(guan)(guan)約(yue)為(wei)0.1V。硅二(er)(er)極(ji)管(guan)(guan)的(de)(de)(de)正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)導(dao)(dao)通(tong)壓(ya)(ya)(ya)(ya)降約(yue)為(wei)0.6~0.8V，鍺二(er)(er)極(ji)管(guan)(guan)的(de)(de)(de)正(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)導(dao)(dao)通(tong)壓(ya)(ya)(ya)(ya)降約(yue)為(wei)0.2~0.3V。

　　反(fan)向(xiang)(xiang)性：外(wai)加反(fan)向(xiang)(xiang)電(dian)壓不(bu)超過一定范(fan)圍(wei)時，通(tong)過二極管的電(dian)流(liu)(liu)是少(shao)數載流(liu)(liu)子漂移(yi)運動(dong)所形(xing)成反(fan)向(xiang)(xiang)電(dian)流(liu)(liu)。由于(yu)反(fan)向(xiang)(xiang)電(dian)流(liu)(liu)很小，二極管處于(yu)截(jie)止狀態。這個反(fan)向(xiang)(xiang)電(dian)流(liu)(liu)又(you)稱為反(fan)向(xiang)(xiang)飽和電(dian)流(liu)(liu)或漏電(dian)流(liu)(liu)，二極管的反(fan)向(xiang)(xiang)飽和電(dian)流(liu)(liu)受溫(wen)度(du)影響很大。一般(ban)硅管的反(fan)向(xiang)(xiang)電(dian)流(liu)(liu)比鍺管小得多，小功率(lv)硅管的反(fan)向(xiang)(xiang)飽和電(dian)流(liu)(liu)在nA數量級，小功率(lv)鍺管在μA數量級。溫(wen)度(du)升高時，半導體(ti)受熱激發，少(shao)數載流(liu)(liu)子數目增加，反(fan)向(xiang)(xiang)飽和電(dian)流(liu)(liu)也隨之增加。

　　擊(ji)(ji)(ji)穿(chuan)(chuan)：外加反向電(dian)(dian)壓超過某一數值時(shi)，反向電(dian)(dian)流(liu)會突然(ran)增大，這種現象稱(cheng)為電(dian)(dian)擊(ji)(ji)(ji)穿(chuan)(chuan)。引起電(dian)(dian)擊(ji)(ji)(ji)穿(chuan)(chuan)的臨界電(dian)(dian)壓稱(cheng)為二極(ji)管(guan)反向擊(ji)(ji)(ji)穿(chuan)(chuan)電(dian)(dian)壓。電(dian)(dian)擊(ji)(ji)(ji)穿(chuan)(chuan)時(shi)二極(ji)管(guan)失去(qu)單向導電(dian)(dian)性(xing)。如果二極(ji)管(guan)沒有(you)因(yin)電(dian)(dian)擊(ji)(ji)(ji)穿(chuan)(chuan)而(er)引起過熱(re)，則(ze)單向導電(dian)(dian)性(xing)不一定會被永(yong)久(jiu)破(po)壞(huai)，在撤除外加電(dian)(dian)壓后，其性(xing)能仍可(ke)恢復，否則(ze)二極(ji)管(guan)就損(sun)壞(huai)了。因(yin)而(er)使用時(shi)應避免(mian)二極(ji)管(guan)外加的反向電(dian)(dian)壓過高。

　　二(er)極(ji)(ji)管是(shi)一種具有(you)單(dan)向(xiang)導電(dian)(dian)(dian)的(de)二(er)端器件，有(you)電(dian)(dian)(dian)子(zi)二(er)極(ji)(ji)管和晶(jing)體(ti)(ti)二(er)極(ji)(ji)管之(zhi)分，電(dian)(dian)(dian)子(zi)二(er)極(ji)(ji)管因為(wei)燈(deng)絲的(de)熱損耗，效率比(bi)晶(jing)體(ti)(ti)二(er)極(ji)(ji)管低，所以現已很少見到，比(bi)較常見和常用的(de)多(duo)是(shi)晶(jing)體(ti)(ti)二(er)極(ji)(ji)管。二(er)極(ji)(ji)管的(de)單(dan)向(xiang)導電(dian)(dian)(dian)特性，幾乎在所有(you)的(de)電(dian)(dian)(dian)子(zi)電(dian)(dian)(dian)路(lu)中，都(dou)要用到半(ban)(ban)導體(ti)(ti)二(er)極(ji)(ji)管，它在許多(duo)的(de)電(dian)(dian)(dian)路(lu)中起著重要的(de)作用，它是(shi)誕(dan)生最早的(de)半(ban)(ban)導體(ti)(ti)器件之(zhi)一，其應用也(ye)非常廣泛。

　　二極(ji)(ji)管(guan)(guan)的(de)(de)管(guan)(guan)壓降(jiang)(jiang)(jiang)：硅(gui)二極(ji)(ji)管(guan)(guan)(不發(fa)(fa)(fa)(fa)(fa)光(guang)類型)正(zheng)(zheng)(zheng)向管(guan)(guan)壓降(jiang)(jiang)(jiang)0.7V，鍺(zang)管(guan)(guan)正(zheng)(zheng)(zheng)向管(guan)(guan)壓降(jiang)(jiang)(jiang)為0.3V，發(fa)(fa)(fa)(fa)(fa)光(guang)二極(ji)(ji)管(guan)(guan)正(zheng)(zheng)(zheng)向管(guan)(guan)壓降(jiang)(jiang)(jiang)會隨不同發(fa)(fa)(fa)(fa)(fa)光(guang)顏色(se)而不同。主要有三種顏色(se)，具體壓降(jiang)(jiang)(jiang)參考(kao)值(zhi)如下：紅色(se)發(fa)(fa)(fa)(fa)(fa)光(guang)二極(ji)(ji)管(guan)(guan)的(de)(de)壓降(jiang)(jiang)(jiang)為2.0--2.2V，黃(huang)色(se)發(fa)(fa)(fa)(fa)(fa)光(guang)二極(ji)(ji)管(guan)(guan)的(de)(de)壓降(jiang)(jiang)(jiang)為1.8—2.0V，綠色(se)發(fa)(fa)(fa)(fa)(fa)光(guang)二極(ji)(ji)管(guan)(guan)的(de)(de)壓降(jiang)(jiang)(jiang)為3.0—3.2V，正(zheng)(zheng)(zheng)常(chang)發(fa)(fa)(fa)(fa)(fa)光(guang)時的(de)(de)額定電流約為20mA。