《模拟电子技术-二极管.ppt》由会员分享，可在线阅读，更多相关《模拟电子技术-二极管.ppt（36页珍藏版）》请在taowenge.com淘文阁网|工程机械CAD图纸|机械工程制图|CAD装配图下载|SolidWorks_CaTia_CAD_UG_PROE_设计图分享下载上搜索。
1、Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 半导体二极管半导体二极管及其基本电路及其基本电路Department of Electronics and Information Science Department of
2、 Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 2.1 半导体的基本知识半导体的基本知识 物质导电物质导电:导体、绝缘体导体、绝缘体和和半导体半导体。半导体半导体:电阻率为电阻率为1010-3-310109 9 cm。常见半导体常见半导体:硅硅Si、锗锗GeGe、砷化镓、砷化镓GaAsGaAs等。1 本征半导体及其导电性 本征半导体：本征半导体：
3、纯净的半导体。纯净的半导体。纯度纯度99.9999999%99.9999999%，常称为，常称为“九个九个9 9”。单晶体单晶体形态形态例如：例如：“单晶硅单晶硅”。Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 硅和锗是
4、四四价价元素。每个原子的四个价价电电子子互相形成共共价价键键,为它们所束缚，形成空间排列有序的晶体,见图2.01。图2.01 硅原子空间排列及共价键结构平面示意图(a)硅晶体的空间排列 (b)共价键结构平面示意图(c)Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information
5、 Science http:/http:/ 图2.02 本征激发和复合的过程（动画2-1）电子空穴对:热、光激发产生的自由电子和空穴对。复合:游离的自由电子回补空穴。动态平衡：温度一定本征激发和复合达到平衡。Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Scie
6、nce http:/http:/ 1）电电子子：价价电子。定向运动形成了电子流，带负电负电；2）空空穴穴：价价电子离开后所留下的空位。它的运动方向与电子流相反，带正电正电。（动画2-2）图2.03 空穴在晶格中的移动Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information
7、Science http:/http:/ 杂质半导体杂质半导体杂质半导体：本征半导体中掺入某些微量元素杂质，所形成的半导体。两种杂质半导体：两种杂质半导体：N型半导体P型半导体杂质：杂质：一般是三价或五价元素（硼，磷）。掺杂目的：掺杂目的：改变半导体的导电性能。Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Elect
8、ronics and Information Science http:/http:/ N型半导体：电子型半导体电子型半导体。(1）N型半导体 N型半导体：本征半导体中掺入五价元素磷形成。N型半导体中自由电子是多数载流子多数载流子,它主要由杂质原子提供；空穴是少数载流子少数载流子,由热激发形成。五价杂质原子，因提供自由电子成为带正电荷的正离子正离子，因此五价杂质原子也称为施主杂质施主杂质。图2.04。Department of Electronics and Information Science Department of Electronics and Information Scienc
9、e Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ P型半导体：本征半导体中掺入三价元素硼形成。P型半导体中空穴是多数载流子，主要由掺杂形成；电子是少数载流子，由热激发形成。空穴很容易俘获电子，使杂质原子成为负离子。三价杂质 因而也称为受主杂质。如图2.05所示。P型半导体：空穴型半导体Department of Electronics and Information Science Department of Ele
10、ctronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 杂质对半导体导电性的影响掺杂质对半导体导电性的影响：掺杂质对半导体导电性的影响：T=300 K室温下室温下,本征硅的电子和空穴浓度本征硅的电子和空穴浓度:n=p=1.41010/cm31 本征硅的原子浓度本征硅的原子浓度:4.961022/cm3 3以上三个浓度基本上依次相差106/cm3。2掺杂后掺杂后
11、N 型半导体中的自由电子浓度型半导体中的自由电子浓度:n=51016/cm3结论：结论：百万分之一的掺杂，导电性能提高百万倍！百万分之一的掺杂，导电性能提高百万倍！Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 将N型半导
12、体和P型半导体合在一起。2.2 PN结的结的形成及特性形成及特性（动画2-3）图2.06 PN结的形成过程1、PN结的形成结的形成Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 将N型半导体和P型半导体合在一起。2.2 P
13、N结的结的形成及特性形成及特性（动画2-3）图2.06 PN结的形成过程1、PN结的形成结的形成Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 浓度差 多子的扩散运动由由杂质离子杂质离子形成空间电荷区 空间电荷区形成内电场
14、 内电场促使少子漂移 内电场阻止多子扩散Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ PN结的导电特性(1)PN结正向特性图2.07 PN结加正向电压时的导电情况及特性 （动画2-4）PN结的正向伏安特性正向导通正向导通
15、Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 图 2.08 PN结加反向电压时的导电情况及特性 （动画2-5）反向截止反向截止Department of Electronics and Information Scien
16、ce Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ P区的电位高于N区的电位，称为加正向电压，简称正偏正偏，PNPN结导电结导电；P区的电位低于N区的电位，称为加反向电压，简称反偏反偏，PNPN结不导电结不导电。结论：结论：PN结具有结具有单向单向导电性导电性!（3）PN结的导电特性结的导电特性Department o
17、f Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ PN结的电容效应(1)势垒电容CB 它由空间电荷区的离子薄层形成。当PN结上压降变化时，该薄层的厚度也随之改变，这相当于PN结中存储的电荷量在变，犹如电容的充放电。图 2.09 势垒电容示意图Dep
18、artment of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ CD是由多子扩散后，在结附近形成的多子浓度梯度分布而形成的，浓度梯度的变化，相当与电容的充放电。图 2.10 扩散电容示意图+-Department of Electronics
19、and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 对高频信号，对高频信号，PN结的单向导电性结的单向导电性受到影响。受到影响。CdCDCB（几个十几个几个十几个pf）Department of Electronics and Information Science Depar
20、tment of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 二极管的结构类型 PN结加上引线和封装，就成为一个二极管。二极管按结构分有三大类。(1)点接触型二极管 PN结面积小，结电容小，用于高频电路。(a)点接触型 图 2.11 二极管的结构示意图2.3 半导体二极管Department of Electronics and Informa
21、tion Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 图 2.11 二极管的结构示意图(c)平面型(3)平面型二极管常用于集成电路工艺中。PN 结面积可大可小。(2)面接触型二极管 PN结面积大，用于工频大电流整流电路。(b)面接触型（4）、二极管的符号Department of Electronic
22、s and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 半导体二极管的伏安特性曲线第一象限:正向特性；第三象限：反向特性。图 2.12 二极管的伏安特性曲线 二极管的伏安特性曲线的近似表达。IS：反向饱和电流；V：二极管两端的电压；VT=kT/q 室温下VT=26 mV。Dep
23、artment of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 硅二极管的死区电压Vth=0.5 V左右，锗二极管的死区电压Vth=0.1 V左右。1)0VVth时，正向电流为零，二极管截止;正向区又分为两段：2)VVth时，正向电流，并按指数
24、规律增长。Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ of Electronics and Information Science Department of Electronics and Information S
25、cience Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 半导体二极管的参数几个主要参数：(1)最大整流电流IF二极管连续工二极管连续工作时，允许通过的最大作时，允许通过的最大电流的平均值。电流的平均值。(2)反向击穿电压VBR 二极管反向电流急剧增加时对应的反向电压值称为反向击穿电压VBR。(3)反向电流IR 硅二极管的反向电流一般在纳安(nA)级；锗二极管在微安(A)级。(4)正向压降VF 硅二极管的正向压降约
26、0.60.8V；锗二极管约0.20.3V。Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 半导体二极管的温度特性温度与反向电流呈指数指数规律。硅管硅管每增加8，反向电流翻一翻翻一翻；锗管锗管每增加12，反向电流翻一翻翻一翻
27、。每增加1，正向压降VF(VD)大约减小2mV，具有负的温度系数负的温度系数。（1）反向情形）反向情形（2）正向情形）正向情形 图 2.13 温度对二极管特性的影响Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 正向导通压
28、降正向导通压降VD=0。反向截止反向截止IR=0Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 正向导通压降VD=0.7V，反向截止IR=0。（3）折线模型）折线模型正向导通压降：VD=0.5V+ID*rD。0.7V0.5
29、VDepartment of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 试画出输出Vo的波形。试画出输出Vo的波形。Department of Electronics and Information Science Department of
30、Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 稳压二极管是工作在反向击穿区的特殊硅二极管。(b)图 2.15 稳压二极管的伏安特性 (a)符号 (b)伏安特性 (c)应用电路(c)用于稳定它两端的输出电压。Department of Electronics and Information Science Department of Electro
31、nics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 在规定的稳压管反向工作电流IZ下，所对应的反向工作电压。动态电阻是从它的反向特性上求取的。rZ愈小，反映稳压管的击穿特性愈陡。rZ=VZ/IZDepartment of Electronics and Information Science Department of Electronics and Informa
32、tion Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ PZM 最大功率损耗取决于PN结的散热等条件。反向时PN结的功耗为 PZ=VZ IZ，由 PZM和VZ可以决定IZmax。(4)最大稳定工作电流 IZmax 和最小稳定工作 电流IZmin 最大稳定工作电流取决于最大耗散功率，即PZmax=VZIZmax。而Izmin对应VZmin。若IZIZmin则不能稳压。VzminDepartment of
33、 Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ of Electronics and Information Science Department of Electronics and Information Science Department
34、of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 八、变容二极管 利用二极管的结电容以及该电容大小与外接电压有关的特点制成。九、光电二极管 使用光敏材料制成，当光照强弱变化时，其反向电流大小亦随之变化。十、发光二极管 有电流通过时，发光二极管对外发光。十一、激光二极管 有电流通过时，激光二极管对外发激光。Department of Electronics and Information Science Department of Electr
35、onics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/