【正文】 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 或者有 ??????????????????????????????????????????1c sc1000kTqUnbbnbpbnbkTqUpenepenbbnbpbnbEEEeLWhLnDqeLpDLWc t hLnDqJChapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 由 ? ? ? ?? ?2200。11 xxLxxeppxpxppCkTqUnCnCnCnCC????????? ?????????????Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 得集電區(qū)的空穴電流密度為 ?????? ??? 10kTqUpCnCpCpCCeLpqDJChapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 據(jù) ? ? ? ?? ?200。12xxeeppxpxppCCLxxkTqUnCnCnCnC??????????????Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 則集電區(qū)的空穴電流密度分布為 ? ?20。12xxeeLpqDJ pCC LxxkTqUpCnCpCpC ??????? ?????Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 隨著 x 增加，集電區(qū)空穴電流密度不斷減小，即集電區(qū)的空穴電流不斷轉(zhuǎn)化為電子電流。 Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 集電極電流密度也應(yīng)等于集電區(qū)內(nèi)電子和空穴的電流密度之和 。 忽略集電結(jié)勢(shì)壘區(qū)中的復(fù)合 ， 可得 Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices ? ? ? ? ? ? ? ???????????????????????100222kTqUpCnCpCbpbnbpCbnBpCnCCCeLpDWnDqxJWJxJxJJChapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 或者 ??????????????????????????????????????????????????11c s c000kTqUpcncpcnbbnbpbnbkTqUnbbnbpbnbCCCeLpDLWc t hLnDqeLWhLnDqJChapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 按照上述方程可以得到均勻基區(qū)晶體管內(nèi)各區(qū)域的電流密度分布 x1 x2 0 Wb JE J nE J pE J nB JC J nC J pC Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices JE 和 JC 的方程描述了均勻基區(qū)晶體管的直流伏安特性 。 它們是均勻基區(qū)晶體管最基本的方程 。 Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 綜上所述，伏安特性表達(dá)式導(dǎo)出時(shí)，作了如下假設(shè) (1) 發(fā)射結(jié)和集電結(jié)是理想突變結(jié)，雜質(zhì)在發(fā)射區(qū)基區(qū)和集電區(qū)都是均勻分布的； Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices (2) 一維晶體管，發(fā)射結(jié)和集電結(jié)平行，且面積相等； (3) 外電壓都降在勢(shì)壘區(qū) ，勢(shì)壘區(qū)以外沒(méi)有電壓降； Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices (4) 發(fā)射區(qū)和集電區(qū)寬度比少數(shù)載流子擴(kuò)散長(zhǎng)度大得多，因此兩區(qū)端側(cè)的少數(shù)載流子密度等于其平衡值； Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices (5) 勢(shì)壘區(qū)寬度比少數(shù)載流子擴(kuò)散長(zhǎng)度小得多 ， 勢(shì)壘區(qū)中的復(fù)合作用可忽略 ，也就是電流通過(guò)勢(shì)壘區(qū)數(shù)值不變； Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices (6) 注入基區(qū)的少數(shù)載流子比基區(qū)的多數(shù)載流子少得多 ， 即不考慮大注入效應(yīng) 。 Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 均勻基區(qū)晶體管的短路電流放大系數(shù) Short Circuit Current amplify Factor of Transistor with uniform Base Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 發(fā)射效率 Emitting Efficiency 根據(jù) npn 晶體管發(fā)射效率 γ 的定義 nEpEpEnEnEEnEJJJJJJJ?????11?Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 把已求得的 JpE 、 JnE 代入上式，有 pepbnbbnepenEpELnDWpDJJ00?Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 根據(jù)嚴(yán)格計(jì)算的結(jié)果，上式成立有兩個(gè)條件： 集電結(jié)短路 ( UC = 0 )； 基區(qū)寬度 Wb 比基區(qū)中電子的擴(kuò)散長(zhǎng)度 Lnb 小得多 Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 類似地， 在后面導(dǎo)出 γ 、 β *、 α * 等量時(shí)， 均要求 UC = 0。 我們稱由 UC = 0 條件導(dǎo)出的電流放大系數(shù)為 短路電流放大系數(shù) 。 Chapter 2 Basic Properties of Bipolar Junction Transistors Fundamental of Semiconductor Devices 得