【二極(ji)管(guan)的作(zuo)用】二極(ji)管(guan)在電路中(zhong)有什么作(zuo)用 二極(ji)管(guan)的特性有哪些(xie)
二極管在電路中有什么作用
二極管是電子元件當(dang)中一(yi)種具(ju)(ju)有兩個電(dian)極的(de)(de)裝置,只允許(xu)電(dian)流(liu)由單一(yi)方(fang)向(xiang)流(liu)過,許(xu)多(duo)的(de)(de)使用(yong)是應用(yong)其整流(liu)的(de)(de)功能。而變容(rong)二(er)極管則用(yong)來當(dang)作電(dian)子式的(de)(de)可調電(dian)容(rong)器。大部(bu)分二(er)極管所具(ju)(ju)備(bei)的(de)(de)電(dian)流(liu)方(fang)向(xiang)性我們(men)通常(chang)稱之為“整流(liu)”功能。二(er)極管最普遍的(de)(de)功能就是只允許(xu)電(dian)流(liu)由單一(yi)方(fang)向(xiang)通過(稱為順向(xiang)偏壓),反向(xiang)時阻斷 (稱為逆向(xiang)偏壓)。因此(ci),二(er)極管可以想成電(dian)子版(ban)的(de)(de)逆止閥。
二極管是最常用的電子元件之一,它最大的特性就是單向導電,也就是電流只可以從二極管的一個方向流過,二極管的作用有整流電路,檢波電路,穩壓電路,各種調制電路,主要都是由二極管來構成的,其原理都很簡單,正是由于二極管等元件的發明,才有我們現在豐富多彩的電子信息世界的誕生,既然二極管的作用這么大那么我們應該如何去檢測這個元件呢,其實很簡單只要用萬用表打到電阻檔測量一下反向電阻如果很小就說明這個二極管是壞的,反向(xiang)電阻如果很大這(zhe)就(jiu)說明這(zhe)個二極管(guan)是好的。
二極管的特性有哪些
正向性
外加正(zheng)(zheng)向(xiang)(xiang)(xiang)電(dian)(dian)壓(ya)時,在(zai)正(zheng)(zheng)向(xiang)(xiang)(xiang)特性的(de)(de)(de)起始(shi)部分,正(zheng)(zheng)向(xiang)(xiang)(xiang)電(dian)(dian)壓(ya)很小,不(bu)(bu)足以克服PN結內電(dian)(dian)場的(de)(de)(de)阻擋作用(yong),正(zheng)(zheng)向(xiang)(xiang)(xiang)電(dian)(dian)流幾乎為(wei)零,這(zhe)一(yi)段稱為(wei)死區(qu)。這(zhe)個不(bu)(bu)能使(shi)二極管(guan)(guan)導(dao)通(tong)(tong)(tong)的(de)(de)(de)正(zheng)(zheng)向(xiang)(xiang)(xiang)電(dian)(dian)壓(ya)稱為(wei)死區(qu)電(dian)(dian)壓(ya)。當(dang)正(zheng)(zheng)向(xiang)(xiang)(xiang)電(dian)(dian)壓(ya)大于死區(qu)電(dian)(dian)壓(ya)以后,PN結內電(dian)(dian)場被克服,二極管(guan)(guan)正(zheng)(zheng)向(xiang)(xiang)(xiang)導(dao)通(tong)(tong)(tong),電(dian)(dian)流隨電(dian)(dian)壓(ya)增(zeng)大而(er)迅(xun)速上(shang)升。在(zai)正(zheng)(zheng)常(chang)使(shi)用(yong)的(de)(de)(de)電(dian)(dian)流范圍內,導(dao)通(tong)(tong)(tong)時二極管(guan)(guan)的(de)(de)(de)端電(dian)(dian)壓(ya)幾乎維持不(bu)(bu)變(bian),這(zhe)個電(dian)(dian)壓(ya)稱為(wei)二極管(guan)(guan)的(de)(de)(de)正(zheng)(zheng)向(xiang)(xiang)(xiang)電(dian)(dian)壓(ya)。當(dang)二極管(guan)(guan)兩(liang)端的(de)(de)(de)正(zheng)(zheng)向(xiang)(xiang)(xiang)電(dian)(dian)壓(ya)超過一(yi)定(ding)數值,內電(dian)(dian)場很快被削弱,特性電(dian)(dian)流迅(xun)速增(zeng)長,二極管(guan)(guan)正(zheng)(zheng)向(xiang)(xiang)(xiang)導(dao)通(tong)(tong)(tong)。叫做(zuo)門坎電(dian)(dian)壓(ya)或(huo)閾值電(dian)(dian)壓(ya),硅(gui)管(guan)(guan)約為(wei)0.5V,鍺(zang)管(guan)(guan)約為(wei)0.1V。硅(gui)二極管(guan)(guan)的(de)(de)(de)正(zheng)(zheng)向(xiang)(xiang)(xiang)導(dao)通(tong)(tong)(tong)壓(ya)降約為(wei)0.6~0.8V,鍺(zang)二極管(guan)(guan)的(de)(de)(de)正(zheng)(zheng)向(xiang)(xiang)(xiang)導(dao)通(tong)(tong)(tong)壓(ya)降約為(wei)0.2~0.3V。
反向性
外加反向電壓不超過一定范圍時,通過二極管的電流是少數載流子漂移運動所形成反向電流。由于反向電流很小,二極管處(chu)于截止(zhi)狀(zhuang)態(tai)。這個(ge)反向(xiang)電流又稱為反向(xiang)飽(bao)和(he)電流或漏電流,二(er)極管(guan)的(de)反向(xiang)飽(bao)和(he)電流受溫度(du)影(ying)響很大。一般硅管(guan)的(de)反向(xiang)電流比鍺管(guan)小(xiao)得多(duo),小(xiao)功率硅管(guan)的(de)反向(xiang)飽(bao)和(he)電流在(zai)nA數(shu)量(liang)級(ji),小(xiao)功率鍺管(guan)在(zai)μA數(shu)量(liang)級(ji)。溫度(du)升高(gao)時,半導體受熱(re)激(ji)發,少數(shu)載流子數(shu)目增加(jia),反向(xiang)飽(bao)和(he)電流也隨之增加(jia)。
反向擊穿
齊納擊穿
反向擊穿(chuan)按機理分為齊(qi)納擊穿(chuan)和雪崩擊穿(chuan)兩種情況。在高(gao)摻(chan)雜濃度(du)的情況下,因勢壘區(qu)寬度(du)很小,反向電壓較大時,破壞了勢壘區(qu)內共價(jia)鍵結構,使(shi)價(jia)電子(zi)脫(tuo)離共價(jia)鍵束縛,產生電子(zi)-空穴(xue)對,致使(shi)電流急劇增大,這種擊穿(chuan)稱為齊(qi)納擊穿(chuan)。如果(guo)摻(chan)雜濃度(du)較低,勢壘區(qu)寬度(du)較寬,不容(rong)易產生齊(qi)納擊穿(chuan)。
雪崩擊穿
另(ling)一種(zhong)擊穿(chuan)為(wei)雪崩擊穿(chuan)。當反向電(dian)(dian)(dian)(dian)壓(ya)增(zeng)加(jia)(jia)到(dao)較大數值時,外加(jia)(jia)電(dian)(dian)(dian)(dian)場(chang)(chang)使電(dian)(dian)(dian)(dian)子(zi)漂移速度加(jia)(jia)快,從(cong)而與共價(jia)(jia)鍵(jian)中的(de)價(jia)(jia)電(dian)(dian)(dian)(dian)子(zi)相(xiang)碰撞(zhuang),把價(jia)(jia)電(dian)(dian)(dian)(dian)子(zi)撞(zhuang)出共價(jia)(jia)鍵(jian),產(chan)生(sheng)新的(de)電(dian)(dian)(dian)(dian)子(zi)-空(kong)穴(xue)對(dui)。新產(chan)生(sheng)的(de)電(dian)(dian)(dian)(dian)子(zi)-空(kong)穴(xue)被電(dian)(dian)(dian)(dian)場(chang)(chang)加(jia)(jia)速后(hou)又撞(zhuang)出其它(ta)價(jia)(jia)電(dian)(dian)(dian)(dian)子(zi),載流子(zi)雪崩式(shi)地(di)增(zeng)加(jia)(jia),致使電(dian)(dian)(dian)(dian)流急(ji)劇增(zeng)加(jia)(jia),這種(zhong)擊穿(chuan)稱為(wei)雪崩擊穿(chuan)。無論哪種(zhong)擊穿(chuan),若對(dui)其電(dian)(dian)(dian)(dian)流不(bu)加(jia)(jia)限制(zhi),都可能造(zao)成PN結永久性損壞。