晶體二(er)極(ji)管(guan)為一(yi)個由p型半導(dao)體和n型半導(dao)體形(xing)成的(de)pn結，在(zai)(zai)其界(jie)面處兩(liang)側形(xing)成空間電(dian)(dian)(dian)(dian)荷層，并建(jian)(jian)有(you)(you)自(zi)建(jian)(jian)電(dian)(dian)(dian)(dian)場。當(dang)不存(cun)在(zai)(zai)外加電(dian)(dian)(dian)(dian)壓(ya)(ya)時，由于pn結兩(liang)邊載流(liu)(liu)子濃度差引(yin)起的(de)擴(kuo)散電(dian)(dian)(dian)(dian)流(liu)(liu)和自(zi)建(jian)(jian)電(dian)(dian)(dian)(dian)場引(yin)起的(de)漂移電(dian)(dian)(dian)(dian)流(liu)(liu)相等而處于電(dian)(dian)(dian)(dian)平(ping)衡狀態。當(dang)外界(jie)有(you)(you)正向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)偏置時，外界(jie)電(dian)(dian)(dian)(dian)場和自(zi)建(jian)(jian)電(dian)(dian)(dian)(dian)場的(de)互相抑消作用使載流(liu)(liu)子的(de)擴(kuo)散電(dian)(dian)(dian)(dian)流(liu)(liu)增(zeng)加引(yin)起了(le)正向(xiang)電(dian)(dian)(dian)(dian)流(liu)(liu)。當(dang)外界(jie)有(you)(you)反(fan)(fan)向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)偏置時，外界(jie)電(dian)(dian)(dian)(dian)場和自(zi)建(jian)(jian)電(dian)(dian)(dian)(dian)場進一(yi)步(bu)加強(qiang)，形(xing)成在(zai)(zai)一(yi)定(ding)反(fan)(fan)向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)范圍(wei)內(nei)與反(fan)(fan)向(xiang)偏置電(dian)(dian)(dian)(dian)壓(ya)(ya)值(zhi)無關的(de)反(fan)(fan)向(xiang)飽和電(dian)(dian)(dian)(dian)流(liu)(liu)I0。當(dang)外加的(de)反(fan)(fan)向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)高到一(yi)定(ding)程度時，pn結空間電(dian)(dian)(dian)(dian)荷層中(zhong)的(de)電(dian)(dian)(dian)(dian)場強(qiang)度達到臨界(jie)值(zhi)產(chan)生載流(liu)(liu)子的(de)倍增(zeng)過程，產(chan)生大(da)量(liang)電(dian)(dian)(dian)(dian)子空穴(xue)對，產(chan)生了(le)數值(zhi)很大(da)的(de)反(fan)(fan)向(xiang)擊(ji)穿(chuan)(chuan)電(dian)(dian)(dian)(dian)流(liu)(liu)，稱為二(er)極(ji)管(guan)的(de)擊(ji)穿(chuan)(chuan)現象。pn結的(de)反(fan)(fan)向(xiang)擊(ji)穿(chuan)(chuan)有(you)(you)齊納擊(ji)穿(chuan)(chuan)和雪崩擊(ji)穿(chuan)(chuan)之分(fen)。

　　二極管的特性

　　正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)性(xing)：二(er)(er)極(ji)管(guan)(guan)(guan)外加正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)時，在正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)特性(xing)的起(qi)始部分，正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)很小，不足以(yi)克(ke)服PN結(jie)內(nei)電(dian)(dian)(dian)(dian)場的阻擋作用，正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)(dian)(dian)(dian)流(liu)(liu)幾(ji)乎為(wei)零，這(zhe)一段稱(cheng)為(wei)死區。這(zhe)個(ge)不能使二(er)(er)極(ji)管(guan)(guan)(guan)導(dao)通的正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)稱(cheng)為(wei)死區電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)。當(dang)正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)大(da)于(yu)死區電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)以(yi)后，PN結(jie)內(nei)電(dian)(dian)(dian)(dian)場被克(ke)服，二(er)(er)極(ji)管(guan)(guan)(guan)正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)導(dao)通，電(dian)(dian)(dian)(dian)流(liu)(liu)隨電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)增大(da)而(er)迅速(su)(su)上升(sheng)。在正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)常使用的電(dian)(dian)(dian)(dian)流(liu)(liu)范圍內(nei)，導(dao)通時二(er)(er)極(ji)管(guan)(guan)(guan)的端電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)幾(ji)乎維(wei)持(chi)不變，這(zhe)個(ge)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)稱(cheng)為(wei)二(er)(er)極(ji)管(guan)(guan)(guan)的正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)。當(dang)二(er)(er)極(ji)管(guan)(guan)(guan)兩端的正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)超過一定數值(zhi)，內(nei)電(dian)(dian)(dian)(dian)場很快被削弱，特性(xing)電(dian)(dian)(dian)(dian)流(liu)(liu)迅速(su)(su)增長(chang)，二(er)(er)極(ji)管(guan)(guan)(guan)正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)導(dao)通。叫做門坎電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)或閾值(zhi)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)，硅管(guan)(guan)(guan)約(yue)為(wei)0.5V，鍺管(guan)(guan)(guan)約(yue)為(wei)0.1V。硅二(er)(er)極(ji)管(guan)(guan)(guan)的正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)導(dao)通壓(ya)(ya)(ya)(ya)降約(yue)為(wei)0.6~0.8V，鍺二(er)(er)極(ji)管(guan)(guan)(guan)的正(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)(zheng)向(xiang)導(dao)通壓(ya)(ya)(ya)(ya)降約(yue)為(wei)0.2~0.3V。

　　反(fan)(fan)向性：外加(jia)反(fan)(fan)向電(dian)(dian)(dian)(dian)壓(ya)不超過(guo)一(yi)定范圍時，通過(guo)二(er)極管(guan)的(de)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)是少數(shu)(shu)載流(liu)(liu)(liu)子漂移運動所形成反(fan)(fan)向電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。由(you)于(yu)反(fan)(fan)向電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)很小(xiao)，二(er)極管(guan)處于(yu)截止狀態。這個反(fan)(fan)向電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)又稱(cheng)為反(fan)(fan)向飽和電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)或漏電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，二(er)極管(guan)的(de)反(fan)(fan)向飽和電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)受溫度影(ying)響(xiang)很大。一(yi)般硅管(guan)的(de)反(fan)(fan)向電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)比(bi)鍺(zang)管(guan)小(xiao)得多，小(xiao)功(gong)率(lv)硅管(guan)的(de)反(fan)(fan)向飽和電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)在nA數(shu)(shu)量(liang)級，小(xiao)功(gong)率(lv)鍺(zang)管(guan)在μA數(shu)(shu)量(liang)級。溫度升高時，半(ban)導體受熱激發，少數(shu)(shu)載流(liu)(liu)(liu)子數(shu)(shu)目增(zeng)加(jia)，反(fan)(fan)向飽和電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)也隨之增(zeng)加(jia)。

　　擊(ji)(ji)穿(chuan)：外(wai)加反向(xiang)(xiang)電(dian)(dian)(dian)壓超過(guo)某一數值時，反向(xiang)(xiang)電(dian)(dian)(dian)流會(hui)突然增大，這種現象稱為電(dian)(dian)(dian)擊(ji)(ji)穿(chuan)。引起(qi)電(dian)(dian)(dian)擊(ji)(ji)穿(chuan)的臨界電(dian)(dian)(dian)壓稱為二(er)(er)極(ji)管(guan)(guan)(guan)反向(xiang)(xiang)擊(ji)(ji)穿(chuan)電(dian)(dian)(dian)壓。電(dian)(dian)(dian)擊(ji)(ji)穿(chuan)時二(er)(er)極(ji)管(guan)(guan)(guan)失(shi)去單向(xiang)(xiang)導電(dian)(dian)(dian)性(xing)。如(ru)果二(er)(er)極(ji)管(guan)(guan)(guan)沒有因(yin)(yin)電(dian)(dian)(dian)擊(ji)(ji)穿(chuan)而(er)引起(qi)過(guo)熱，則單向(xiang)(xiang)導電(dian)(dian)(dian)性(xing)不一定會(hui)被永(yong)久(jiu)破(po)壞(huai)，在(zai)撤(che)除外(wai)加電(dian)(dian)(dian)壓后，其性(xing)能仍可恢復，否則二(er)(er)極(ji)管(guan)(guan)(guan)就損壞(huai)了。因(yin)(yin)而(er)使用時應避免二(er)(er)極(ji)管(guan)(guan)(guan)外(wai)加的反向(xiang)(xiang)電(dian)(dian)(dian)壓過(guo)高(gao)。

　　二(er)(er)(er)極(ji)(ji)(ji)管(guan)(guan)是一種(zhong)具有(you)單向導(dao)電(dian)(dian)(dian)的(de)(de)二(er)(er)(er)端器件(jian)，有(you)電(dian)(dian)(dian)子(zi)二(er)(er)(er)極(ji)(ji)(ji)管(guan)(guan)和(he)晶(jing)體(ti)二(er)(er)(er)極(ji)(ji)(ji)管(guan)(guan)之分，電(dian)(dian)(dian)子(zi)二(er)(er)(er)極(ji)(ji)(ji)管(guan)(guan)因為(wei)燈絲的(de)(de)熱(re)損耗(hao)，效率比(bi)晶(jing)體(ti)二(er)(er)(er)極(ji)(ji)(ji)管(guan)(guan)低，所以現(xian)已很少見到，比(bi)較常(chang)見和(he)常(chang)用(yong)(yong)的(de)(de)多(duo)是晶(jing)體(ti)二(er)(er)(er)極(ji)(ji)(ji)管(guan)(guan)。二(er)(er)(er)極(ji)(ji)(ji)管(guan)(guan)的(de)(de)單向導(dao)電(dian)(dian)(dian)特性(xing)，幾乎在(zai)所有(you)的(de)(de)電(dian)(dian)(dian)子(zi)電(dian)(dian)(dian)路中(zhong)，都要(yao)用(yong)(yong)到半導(dao)體(ti)二(er)(er)(er)極(ji)(ji)(ji)管(guan)(guan)，它在(zai)許多(duo)的(de)(de)電(dian)(dian)(dian)路中(zhong)起著重要(yao)的(de)(de)作(zuo)用(yong)(yong)，它是誕生最早的(de)(de)半導(dao)體(ti)器件(jian)之一，其應用(yong)(yong)也非常(chang)廣泛。

　　二(er)極(ji)(ji)(ji)(ji)管(guan)(guan)(guan)的(de)管(guan)(guan)(guan)壓降(jiang)(jiang)：硅二(er)極(ji)(ji)(ji)(ji)管(guan)(guan)(guan)(不(bu)(bu)發(fa)光(guang)類型)正(zheng)向管(guan)(guan)(guan)壓降(jiang)(jiang)0.7V，鍺管(guan)(guan)(guan)正(zheng)向管(guan)(guan)(guan)壓降(jiang)(jiang)為0.3V，發(fa)光(guang)二(er)極(ji)(ji)(ji)(ji)管(guan)(guan)(guan)正(zheng)向管(guan)(guan)(guan)壓降(jiang)(jiang)會隨不(bu)(bu)同發(fa)光(guang)顏(yan)色而不(bu)(bu)同。主(zhu)要有三種顏(yan)色，具體壓降(jiang)(jiang)參考值如下(xia)：紅色發(fa)光(guang)二(er)極(ji)(ji)(ji)(ji)管(guan)(guan)(guan)的(de)壓降(jiang)(jiang)為2.0--2.2V，黃色發(fa)光(guang)二(er)極(ji)(ji)(ji)(ji)管(guan)(guan)(guan)的(de)壓降(jiang)(jiang)為1.8—2.0V，綠色發(fa)光(guang)二(er)極(ji)(ji)(ji)(ji)管(guan)(guan)(guan)的(de)壓降(jiang)(jiang)為3.0—3.2V，正(zheng)常發(fa)光(guang)時的(de)額定電流約為20mA。