晶體(ti)二極(ji)管為一個(ge)由p型(xing)半導體(ti)和(he)n型(xing)半導體(ti)形(xing)(xing)成的(de)(de)pn結，在(zai)其界面處兩(liang)側形(xing)(xing)成空(kong)(kong)間(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷層，并建(jian)(jian)有(you)自(zi)建(jian)(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場。當(dang)不存(cun)在(zai)外(wai)加電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)時，由于pn結兩(liang)邊載流(liu)子濃度(du)差(cha)引起的(de)(de)擴(kuo)散電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)和(he)自(zi)建(jian)(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場引起的(de)(de)漂(piao)移電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)相(xiang)等而(er)處于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)衡狀態。當(dang)外(wai)界有(you)正向(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)偏置(zhi)時，外(wai)界電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場和(he)自(zi)建(jian)(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場的(de)(de)互相(xiang)抑消作用使載流(liu)子的(de)(de)擴(kuo)散電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)增(zeng)加引起了正向(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。當(dang)外(wai)界有(you)反(fan)向(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)偏置(zhi)時，外(wai)界電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場和(he)自(zi)建(jian)(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場進一步加強(qiang)，形(xing)(xing)成在(zai)一定反(fan)向(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)范圍內(nei)與反(fan)向(xiang)偏置(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)值無關的(de)(de)反(fan)向(xiang)飽和(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)I0。當(dang)外(wai)加的(de)(de)反(fan)向(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)高到一定程(cheng)度(du)時，pn結空(kong)(kong)間(jian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷層中(zhong)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場強(qiang)度(du)達到臨界值產(chan)生(sheng)載流(liu)子的(de)(de)倍增(zeng)過程(cheng)，產(chan)生(sheng)大(da)量電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)子空(kong)(kong)穴對，產(chan)生(sheng)了數值很大(da)的(de)(de)反(fan)向(xiang)擊(ji)穿(chuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，稱為二極(ji)管的(de)(de)擊(ji)穿(chuan)現象。pn結的(de)(de)反(fan)向(xiang)擊(ji)穿(chuan)有(you)齊納(na)擊(ji)穿(chuan)和(he)雪(xue)崩(beng)擊(ji)穿(chuan)之(zhi)分(fen)。

　　二極管的特性

　　正(zheng)(zheng)向性(xing)：二極(ji)管(guan)(guan)外加(jia)正(zheng)(zheng)向電(dian)(dian)壓(ya)時，在正(zheng)(zheng)向特(te)性(xing)的(de)(de)起始部分，正(zheng)(zheng)向電(dian)(dian)壓(ya)很小，不足以克服(fu)PN結內(nei)電(dian)(dian)場的(de)(de)阻擋(dang)作用(yong)(yong)，正(zheng)(zheng)向電(dian)(dian)流(liu)幾乎為(wei)零(ling)，這(zhe)一(yi)段(duan)稱(cheng)(cheng)(cheng)為(wei)死(si)區(qu)。這(zhe)個(ge)不能(neng)使二極(ji)管(guan)(guan)導(dao)通(tong)(tong)的(de)(de)正(zheng)(zheng)向電(dian)(dian)壓(ya)稱(cheng)(cheng)(cheng)為(wei)死(si)區(qu)電(dian)(dian)壓(ya)。當正(zheng)(zheng)向電(dian)(dian)壓(ya)大于死(si)區(qu)電(dian)(dian)壓(ya)以后，PN結內(nei)電(dian)(dian)場被克服(fu)，二極(ji)管(guan)(guan)正(zheng)(zheng)向導(dao)通(tong)(tong)，電(dian)(dian)流(liu)隨電(dian)(dian)壓(ya)增大而迅速上升。在正(zheng)(zheng)常使用(yong)(yong)的(de)(de)電(dian)(dian)流(liu)范(fan)圍(wei)內(nei)，導(dao)通(tong)(tong)時二極(ji)管(guan)(guan)的(de)(de)端電(dian)(dian)壓(ya)幾乎維持不變，這(zhe)個(ge)電(dian)(dian)壓(ya)稱(cheng)(cheng)(cheng)為(wei)二極(ji)管(guan)(guan)的(de)(de)正(zheng)(zheng)向電(dian)(dian)壓(ya)。當二極(ji)管(guan)(guan)兩端的(de)(de)正(zheng)(zheng)向電(dian)(dian)壓(ya)超過(guo)一(yi)定(ding)數值(zhi)，內(nei)電(dian)(dian)場很快被削弱，特(te)性(xing)電(dian)(dian)流(liu)迅速增長，二極(ji)管(guan)(guan)正(zheng)(zheng)向導(dao)通(tong)(tong)。叫做門坎(kan)電(dian)(dian)壓(ya)或閾(yu)值(zhi)電(dian)(dian)壓(ya)，硅管(guan)(guan)約為(wei)0.5V，鍺(zang)管(guan)(guan)約為(wei)0.1V。硅二極(ji)管(guan)(guan)的(de)(de)正(zheng)(zheng)向導(dao)通(tong)(tong)壓(ya)降約為(wei)0.6~0.8V，鍺(zang)二極(ji)管(guan)(guan)的(de)(de)正(zheng)(zheng)向導(dao)通(tong)(tong)壓(ya)降約為(wei)0.2~0.3V。

　　反(fan)(fan)向(xiang)(xiang)性：外(wai)加反(fan)(fan)向(xiang)(xiang)電壓不超過一定范圍(wei)時，通(tong)過二極(ji)管的電流(liu)(liu)(liu)是少數載流(liu)(liu)(liu)子漂移運(yun)動所形成反(fan)(fan)向(xiang)(xiang)電流(liu)(liu)(liu)。由于(yu)反(fan)(fan)向(xiang)(xiang)電流(liu)(liu)(liu)很(hen)小(xiao)，二極(ji)管處于(yu)截止狀態。這個(ge)反(fan)(fan)向(xiang)(xiang)電流(liu)(liu)(liu)又稱(cheng)為(wei)反(fan)(fan)向(xiang)(xiang)飽和電流(liu)(liu)(liu)或(huo)漏電流(liu)(liu)(liu)，二極(ji)管的反(fan)(fan)向(xiang)(xiang)飽和電流(liu)(liu)(liu)受溫(wen)度影響(xiang)很(hen)大。一般(ban)硅管的反(fan)(fan)向(xiang)(xiang)電流(liu)(liu)(liu)比鍺管小(xiao)得多(duo)，小(xiao)功率硅管的反(fan)(fan)向(xiang)(xiang)飽和電流(liu)(liu)(liu)在nA數量(liang)級(ji)，小(xiao)功率鍺管在μA數量(liang)級(ji)。溫(wen)度升高時，半導體受熱(re)激發(fa)，少數載流(liu)(liu)(liu)子數目增加，反(fan)(fan)向(xiang)(xiang)飽和電流(liu)(liu)(liu)也隨(sui)之增加。

　　擊穿(chuan)：外(wai)加反(fan)向電(dian)(dian)壓超過(guo)(guo)某一(yi)數值(zhi)時(shi)，反(fan)向電(dian)(dian)流會突然增大(da)，這種現(xian)象稱(cheng)為電(dian)(dian)擊穿(chuan)。引(yin)(yin)起電(dian)(dian)擊穿(chuan)的臨界電(dian)(dian)壓稱(cheng)為二極(ji)管(guan)反(fan)向擊穿(chuan)電(dian)(dian)壓。電(dian)(dian)擊穿(chuan)時(shi)二極(ji)管(guan)失(shi)去(qu)單向導電(dian)(dian)性(xing)。如果(guo)二極(ji)管(guan)沒(mei)有因電(dian)(dian)擊穿(chuan)而引(yin)(yin)起過(guo)(guo)熱(re)，則單向導電(dian)(dian)性(xing)不一(yi)定會被永久(jiu)破壞，在撤除外(wai)加電(dian)(dian)壓后，其性(xing)能(neng)仍可恢復，否(fou)則二極(ji)管(guan)就損壞了。因而使用(yong)時(shi)應避免二極(ji)管(guan)外(wai)加的反(fan)向電(dian)(dian)壓過(guo)(guo)高(gao)。

　　二(er)(er)極管(guan)是(shi)一種(zhong)具(ju)有單向導(dao)電(dian)的二(er)(er)端器(qi)(qi)件，有電(dian)子二(er)(er)極管(guan)和晶體(ti)(ti)二(er)(er)極管(guan)之(zhi)分，電(dian)子二(er)(er)極管(guan)因為燈絲的熱損耗，效率比(bi)晶體(ti)(ti)二(er)(er)極管(guan)低，所(suo)以現已很少(shao)見(jian)到(dao)，比(bi)較常見(jian)和常用(yong)的多(duo)是(shi)晶體(ti)(ti)二(er)(er)極管(guan)。二(er)(er)極管(guan)的單向導(dao)電(dian)特性，幾乎在(zai)所(suo)有的電(dian)子電(dian)路中(zhong)，都要用(yong)到(dao)半(ban)導(dao)體(ti)(ti)二(er)(er)極管(guan)，它在(zai)許多(duo)的電(dian)路中(zhong)起著重要的作用(yong)，它是(shi)誕生最早的半(ban)導(dao)體(ti)(ti)器(qi)(qi)件之(zhi)一，其(qi)應用(yong)也(ye)非常廣泛。

　　二(er)極(ji)管(guan)(guan)(guan)(guan)(guan)(guan)的管(guan)(guan)(guan)(guan)(guan)(guan)壓(ya)(ya)降：硅(gui)二(er)極(ji)管(guan)(guan)(guan)(guan)(guan)(guan)(不發(fa)(fa)(fa)光(guang)類(lei)型)正向(xiang)管(guan)(guan)(guan)(guan)(guan)(guan)壓(ya)(ya)降0.7V，鍺(zang)管(guan)(guan)(guan)(guan)(guan)(guan)正向(xiang)管(guan)(guan)(guan)(guan)(guan)(guan)壓(ya)(ya)降為(wei)(wei)0.3V，發(fa)(fa)(fa)光(guang)二(er)極(ji)管(guan)(guan)(guan)(guan)(guan)(guan)正向(xiang)管(guan)(guan)(guan)(guan)(guan)(guan)壓(ya)(ya)降會隨不同發(fa)(fa)(fa)光(guang)顏(yan)色而不同。主要有三(san)種顏(yan)色，具體壓(ya)(ya)降參考值如下(xia)：紅色發(fa)(fa)(fa)光(guang)二(er)極(ji)管(guan)(guan)(guan)(guan)(guan)(guan)的壓(ya)(ya)降為(wei)(wei)2.0--2.2V，黃色發(fa)(fa)(fa)光(guang)二(er)極(ji)管(guan)(guan)(guan)(guan)(guan)(guan)的壓(ya)(ya)降為(wei)(wei)1.8—2.0V，綠色發(fa)(fa)(fa)光(guang)二(er)極(ji)管(guan)(guan)(guan)(guan)(guan)(guan)的壓(ya)(ya)降為(wei)(wei)3.0—3.2V，正常(chang)發(fa)(fa)(fa)光(guang)時的額定電流約為(wei)(wei)20mA。