晶體三極管妙用保證了(le)壓力校驗儀的穩定性(xing)

半導體三極管

晶(jing)(jing)體(ti)三(san)極(ji)管(guan)(guan)(guan)（簡(jian)稱(cheng)三(san)極(ji)管(guan)(guan)(guan)）和(he)場效(xiao)應(ying)(ying)晶(jing)(jing)體(ti)管(guan)(guan)(guan)（簡(jian)稱(cheng)場效(xiao)應(ying)(ying)管(guan)(guan)(guan)）都是具有放大作用(yong)和(he)開關特(te)性的(de)(de)半導體(ti)三(san)極(ji)管(guan)(guan)(guan)，是電子設備中的(de)(de)核(he)心器(qi)(qi)件(jian)之一，應(ying)(ying)用(yong)十分廣泛。晶(jing)(jing)體(ti)三(san)極(ji)管(guan)(guan)(guan)和(he)場效(xiao)應(ying)(ying)晶(jing)(jing)體(ti)管(guan)(guan)(guan)雖(sui)然外形相(xiang)同(tong)，但工作原理(li)卻截然不(bu)同(tong)，普通晶(jing)(jing)體(ti)三(san)極(ji)管(guan)(guan)(guan)是電流(liu)控制(zhi)(zhi)型(xing)器(qi)(qi)件(jian)，而場效(xiao)應(ying)(ying)晶(jing)(jing)體(ti)管(guan)(guan)(guan)是電壓控制(zhi)(zhi)型(xing)器(qi)(qi)件(jian)

單(dan)結(jie)(jie)(jie)晶(jing)(jing)體(ti)管(guan)(guan)(guan)(guan)（簡稱(cheng)單(dan)結(jie)(jie)(jie)管(guan)(guan)(guan)(guan)）雖具有(you)3個(ge)電極(ji)(ji)(ji)，但按其內部僅有(you)一個(ge)pn結(jie)(jie)(jie)來區分(fen)、可(ke)劃歸為一種特殊的晶(jing)(jing)體(ti)二極(ji)(ji)(ji)管(guan)(guan)(guan)(guan)、它與(yu)普通晶(jing)(jing)體(ti)三極(ji)(ji)(ji)管(guan)(guan)(guan)(guan)的不同之(zhi)處在于只有(you)一個(ge)發射極(ji)(ji)(ji)和(he)兩個(ge)基極(ji)(ji)(ji)，卻(que)沒有(you)集電極(ji)(ji)(ji)，所以(yi)單(dan)結(jie)(jie)(jie)晶(jing)(jing)體(ti)管(guan)(guan)(guan)(guan)也稱(cheng)為雙基極(ji)(ji)(ji)二極(ji)(ji)(ji)管(guan)(guan)(guan)(guan)，單(dan)結(jie)(jie)(jie)晶(jing)(jing)體(ti)管(guan)(guan)(guan)(guan)具有(you)個(ge)重要的電氣性(xing)能————負(fu)阻特性(xing)，利用其可(ke)以(yi)方便地組成弛張振蕩器、延時電路(lu)和(he)觸發電路(lu)等，而且(qie)電路(lu)非常(chang)簡單(dan)。

神通廣大(da)的晶體三極(ji)管

 性能優良(liang)的場效應晶體管

與眾不同的單(dan)結晶(jing)體管

神通廣大的(de)晶體三極管

晶(jing)(jing)體(ti)三極(ji)管(guan)簡稱晶(jing)(jing)體(ti)管(guan)或三極(ji)管(guan)，是(shi)(shi)一種具有兩個pn結的半導體(ti)器件(jian)。晶(jing)(jing)體(ti)三極(ji)管(guan)的最大特點是(shi)(shi)具有電流(liu)(liu)放大及控制(zhi)作用(yong)(yong)，它(ta)是(shi)(shi)在電子線路(lu)中(zhong)被廣泛(fan)使(shi)用(yong)(yong)的重(zhong)要(yao)電流(liu)(liu)控制(zhi)型器件(jian)。

利用晶體(ti)三極(ji)(ji)管的特性，可以(yi)組(zu)成放(fang)大、振蕩、開關(guan)等各種功能(neng)的電子電路。從某種意(yi)義上講，許(xu)(xu)多電子電路離開了(le)晶體(ti)三極(ji)(ji)管將會“一事無(wu)成"，電路中的電阻器(qi)(qi)、電容器(qi)(qi)、電感器(qi)(qi)等許(xu)(xu)多元件都(dou)是(shi)為晶體(ti)三極(ji)(ji)管服務的。

種類和結構

常(chang)用晶體三(san)極(ji)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)的(de)實(shi)物(wu)外形如圖所示。晶體三(san)極(ji)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)按(an)(an)(an)制造材(cai)(cai)料不同(tong)(tong)(tong)，可分(fen)為(wei)硅管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)、鍺管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)和(he)化合物(wu)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)；按(an)(an)(an)pn結組合（即導電(dian)極(ji)性(xing)）不同(tong)(tong)(tong)，可分(fen)為(wei)pnp型和(he)npn型兩大(da)類；按(an)(an)(an)特征頻(pin)率不同(tong)(tong)(tong)，可分(fen)為(wei)超(chao)高頻(pin)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)（≥300mhz）、高頻(pin)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)（≥30mhz）、中頻(pin)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)（≥3mhz）和(he)低頻(pin)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)（<3mhz）按(an)(an)(an)功(gong)率大(da)小(xiao)劃分(fen)，可分(fen)為(wei)小(xiao)功(gong)率管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)（<0.5w）、中功(gong)率管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)（0.5~1w）和(he)大(da)功(gong)率管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)（>1w）；按(an)(an)(an)封裝(zhuang)材(cai)(cai)料不同(tong)(tong)(tong)，可分(fen)為(wei)塑料封裝(zhuang)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)、金屬殼封裝(zhuang)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)、玻(bo)璃(li)殼封裝(zhuang)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)和(he)陶瓷環氧封裝(zhuang)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)等；按(an)(an)(an)用途可分(fen)為(wei)低頻(pin)放(fang)大(da)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)、高頻(pin)放(fang)大(da)管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)、開關管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)、低噪聲管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)、高反壓管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)、復合管(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)(guan)等。

圖常見晶體三極管的實物(wu)外形圖

雖然(ran)晶體(ti)三(san)(san)(san)極(ji)(ji)(ji)(ji)管(guan)(guan)的(de)種類和(he)型(xing)號很(hen)(hen)多，但它們(men)的(de)內部構(gou)(gou)造(zao)基本相同。晶體(ti)三(san)(san)(san)極(ji)(ji)(ji)(ji)管(guan)(guan)的(de)內部結(jie)(jie)構(gou)(gou)示意圖和(he)各部分(fen)名稱(cheng)見圖。每一只晶體(ti)三(san)(san)(san)極(ji)(ji)(ji)(ji)管(guan)(guan)都有3條引腳，分(fen)別叫作發射極(ji)(ji)(ji)(ji)、基極(ji)(ji)(ji)(ji)和(he)集電極(ji)(ji)(ji)(ji)，依次用字母e、b、c表示。晶體(ti)三(san)(san)(san)極(ji)(ji)(ji)(ji)管(guan)(guan)內部管(guan)(guan)芯是兩(liang)(liang)個靠得(de)極(ji)(ji)(ji)(ji)近的(de)pn結(jie)(jie)，管(guan)(guan)子具有兩(liang)(liang)種類型(xing)∶如果把一小塊半導體(ti)中(zhong)間制成很(hen)(hen)薄的(de)n型(xing)區(qu)，兩(liang)(liang)邊制成p型(xing)區(qu)，就做成了pnp型(xing)三(san)(san)(san)極(ji)(ji)(ji)(ji)管(guan)(guan)；如果中(zhong)間制成很(hen)(hen)薄的(de)p型(xing)區(qu)，兩(liang)(liang)邊制成n型(xing)區(qu)，就做成了npn型(xing)三(san)(san)(san)極(ji)(ji)(ji)(ji)管(guan)(guan)。無論哪(na)一種類型(xing)，構(gou)(gou)成晶體(ti)三(san)(san)(san)極(ji)(ji)(ji)(ji)管(guan)(guan)的(de)兩(liang)(liang)個pn結(jie)(jie)均分(fen)別稱(cheng)為集電結(jie)(jie)(c、b極(ji)(ji)(ji)(ji)之(zhi)間)和(he)發射結(jie)(jie)（b、e極(ji)(ji)(ji)(ji)之(zhi)間)。

基本特性

晶(jing)體(ti)三極(ji)管在電(dian)(dian)路中(zhong)的(de)(de)工作情況(kuang)，可(ke)以通(tong)過實(shi)(shi)驗(yan)來說(shuo)明，實(shi)(shi)驗(yan)電(dian)(dian)路如圖所示。這(zhe)里(li)我們使用(yong)的(de)(de)是一只(zhi)npn型(xing)(xing)三極(ji)管，若(ruo)用(yong)pnp型(xing)(xing)管，除電(dian)(dian)源極(ji)性要調(diao)換外，其他情況(kuang)與實(shi)(shi)驗(yan)結果(guo)都基本相同。為了(le)說(shuo)明方便(bian)，電(dian)(dian)路中(zhong)我們畫出了(le)晶(jing)體(ti)三極(ji)管的(de)(de)內部(bu)結構。

圖晶體三極管實驗電路

圖中，晶體三極(ji)(ji)管基(ji)極(ji)(ji)b與發射(she)(she)(she)(she)極(ji)(ji)e之(zhi)間(jian)接入電(dian)(dian)池go,基(ji)極(ji)(ji)接電(dian)(dian)池的(de)(de)(de)正極(ji)(ji)，發射(she)(she)(she)(she)極(ji)(ji)接電(dian)(dian)池的(de)(de)(de)負極(ji)(ji)。這時b、e之(zhi)間(jian)(發射(she)(she)(she)(she)結(jie))加(jia)的(de)(de)(de)是正向電(dian)(dian)壓。從基(ji)極(ji)(ji)電(dian)(dian)路中串(chuan)聯的(de)(de)(de)電(dian)(dian)流(liu)表可以讀出電(dian)(dian)流(liu)的(de)(de)(de)大小，這個電(dian)(dian)流(liu)叫(jiao)做基(ji)極(ji)(ji)電(dian)(dian)流(liu)/。。如果我們把電(dian)(dian)池gg的(de)(de)(de)正、負極(ji)(ji)對換一下(xia)，發射(she)(she)(she)(she)結(jie)上就加(jia)了反(fan)向電(dian)(dian)壓。從pn結(jie)原(yuan)理(li)可知，這時電(dian)(dian)流(liu)是不能(neng)通過的(de)(de)(de)，也就是說沒(mei)有基(ji)極(ji)(ji)電(dian)(dian)流(liu)，即(ji)1=0。可見，晶體三極(ji)(ji)管的(de)(de)(de)發射(she)(she)(she)(she)結(jie)具(ju)有單向導電(dian)(dian)性。

再來看發(fa)(fa)射(she)極(ji)e與集(ji)電(dian)(dian)(dian)(dian)(dian)極(ji)c之(zhi)間(jian)的情況：電(dian)(dian)(dian)(dian)(dian)路中加了電(dian)(dian)(dian)(dian)(dian)池(chi)gc,電(dian)(dian)(dian)(dian)(dian)池(chi)正極(ji)接(jie)集(ji)電(dian)(dian)(dian)(dian)(dian)極(ji)，負極(ji)接(jie)發(fa)(fa)射(she)極(ji)。這個電(dian)(dian)(dian)(dian)(dian)壓(ya)叫集(ji)電(dian)(dian)(dian)(dian)(dian)極(ji)c與發(fa)(fa)射(she)極(ji)e之(zhi)間(jian)的反向電(dian)(dian)(dian)(dian)(dian)壓(ya)。同樣，用串聯在集(ji)電(dian)(dian)(dian)(dian)(dian)極(ji)上(shang)的電(dian)(dian)(dian)(dian)(dian)流(liu)表(biao)測(ce)量集(ji)電(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)流(liu)/。,我們(men)會發(fa)(fa)現：當基極(ji)電(dian)(dian)(dian)(dian)(dian)流(liu)/。等(deng)于零時(shi)，集(ji)電(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)流(liu)/。極(ji)小(xiao)，甚至幾乎等(deng)于零。一旦(dan)基極(ji)電(dian)(dian)(dian)(dian)(dian)流(liu)/.產生，集(ji)電(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)流(liu)會立即(ji)迅(xun)速增(zeng)大。

基(ji)極(ji)電(dian)(dian)流(liu)(liu)的(de)(de)(de)有無，可以控制(zhi)集電(dian)(dian)極(ji)電(dian)(dian)流(liu)(liu)的(de)(de)(de)通斷——這是晶(jing)體三(san)極(ji)管的(de)(de)(de)一(yi)個(ge)重要特性。我們繼(ji)續進(jin)行實驗：將電(dian)(dian)路中的(de)(de)(de)基(ji)極(ji)電(dian)(dian)阻r,改用(yong)一(yi)個(ge)電(dian)(dian)位器(qi)。通過調節ro,使基(ji)極(ji)電(dian)(dian)流(liu)(liu)大(da)小(xiao)發生變(bian)(bian)化，可以發現集電(dian)(dian)極(ji)電(dian)(dian)流(liu)(liu)/。的(de)(de)(de)大(da)小(xiao)也會(hui)隨之發生變(bian)(bian)化。但(dan)是，比較兩個(ge)電(dian)(dian)流(liu)(liu)表讀數，不難發現，當/,在幾十微安范圍(wei)內(nei)變(bian)(bian)動時(shi)，/6的(de)(de)(de)變(bian)(bian)動范圍(wei)達到幾毫安。實驗和理論分(fen)析(xi)都(dou)證明，晶(jing)體三(san)極(ji)管對電(dian)(dian)流(liu)(liu)的(de)(de)(de)變(bian)(bian)化有“放大(da)"作用(yong)。

晶(jing)(jing)體三極(ji)(ji)管基極(ji)(ji)電(dian)流的(de)微小變(bian)化，會使集電(dian)極(ji)(ji)電(dian)流發生很(hen)大變(bian)化——這是晶(jing)(jing)體三極(ji)(ji)管的(de)另一(yi)個(ge)重要特(te)性(xing)——放(fang)大特(te)性(xing)。

晶(jing)體(ti)(ti)三(san)極管工作(zuo)時(shi)，除去基極b和集(ji)電(dian)(dian)(dian)極c外，發(fa)(fa)射(she)(she)極e也(ye)有(you)(you)電(dian)(dian)(dian)流(liu)通(tong)過(guo)。圖形象(xiang)地表示了(le)晶(jing)體(ti)(ti)三(san)極管內部的電(dian)(dian)(dian)流(liu)分配關系。我們可以大致這(zhe)樣來理解：以npn型管為(wei)例，在發(fa)(fa)射(she)(she)結正向(xiang)(xiang)電(dian)(dian)(dian)壓作(zuo)用下，發(fa)(fa)射(she)(she)極“發(fa)(fa)射(she)(she)"電(dian)(dian)(dian)子(zi)，電(dian)(dian)(dian)子(zi)經(jing)過(guo)基區時(shi)，一小(xiao)部分形成(cheng)基極電(dian)(dian)(dian)流(liu)，而大部分繼續飛向(xiang)(xiang)集(ji)電(dian)(dian)(dian)極，形成(cheng)集(ji)電(dian)(dian)(dian)極電(dian)(dian)(dian)流(liu)。由(you)于規定電(dian)(dian)(dian)流(liu)的方向(xiang)(xiang)是與電(dian)(dian)(dian)子(zi)運動方向(xiang)(xiang)相反的，所(suo)(suo)以圖中代(dai)表電(dian)(dian)(dian)流(liu)方向(xiang)(xiang)的箭頭(tou)分別由(you)集(ji)電(dian)(dian)(dian)極和基極指向(xiang)(xiang)發(fa)(fa)射(she)(she)極。我們把通(tong)過(guo)發(fa)(fa)射(she)(she)極的電(dian)(dian)(dian)流(liu)叫做發(fa)(fa)射(she)(she)極電(dian)(dian)(dian)流(liu)/0。晶(jing)體(ti)(ti)三(san)極管中，總有(you)(you)/0=1。+1這(zhe)個關系。又由(you)于兒比/。要小(xiao)得多，所(suo)(suo)以在一般情況下也(ye)可以近(jin)似地認(ren)為(wei)/?=1。