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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:/ 概概 述述5.2 乙类互补对称功率放大电路乙类互补对称功率放大电路 5.3 甲乙类互补对称功率放大电路甲乙类互补对称功率放大电路u 甲甲乙类双电源互补对称电路乙类双电源互补对
2、称电路u 甲甲乙类单电源互补对称电路乙类单电源互补对称电路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:/ 扩音系统扩音系统执行机构执行机构功率放大器的作用：功率放大器的作用： 用作放大电路的用作放大电路的输出级输出级，以，
3、以驱驱动动执行机构。如使扬声器发声、继电器动作、执行机构。如使扬声器发声、继电器动作、 仪表仪表指针偏转等。指针偏转等。 5.1 5.1 概述概述功功率率放放大大电电压压放放大大信信号号提提取取Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science htt
4、p:/http:/ 功放电路的特点功放电路的特点（2） 功放电路中电流、电压都比较大，必须注意功放电路中电流、电压都比较大，必须注意电路参数不能超过晶体管的极限值电路参数不能超过晶体管的极限值: ICM 、VCEM 、 PCM 。 ICMPCMVCEMIcvce（1）输出功率输出功率Po尽可能大尽可能大Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Scienc
5、e Department of Electronics and Information Science http:/http:/ 电流、电压信号比较大，必须注意防止波形失真。电流、电压信号比较大，必须注意防止波形失真。(4) 电源提供的能量尽可能转换给负载，减少晶体管及电源提供的能量尽可能转换给负载，减少晶体管及线路上的损失。即注意提高电路的效率（线路上的损失。即注意提高电路的效率（ ）。）。Pomax : 负载上得到的交流信号功率。负载上得到的交流信号功率。PV ： 电源提供的直流功率。电源提供的直流功率。（5）功放管散热和保护问题）功放管散热和保护问题Department of Elect
6、ronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 甲类功率放大器分析甲类功率放大器分析三极管的静态功耗：三极管的静态功耗：若若Department of Electronics and Information Science Department of Elec
7、tronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 在输出特性曲线上，正在输出特性曲线上，正好是三角形好是三角形 ABQ的面积，这的面积，这一三角形称为一三角形称为功率三角形功率三角形。 要想要想PO大，就要使功率三角形的大，就要使功率三角形的面积大，即必须使面积大，即必须使Vom 和和Iom 都要大。都要大。最大输出功率最大输出功率Department of
8、 Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 输出功率小输出功率小 静态功率大，效率低，但失真小静态功率大，效率低，但失真小三三. 几种工作状态几种工作状态 根根据据在在正正弦弦信信号号整整个个周周期期内内的的三三极极管管导导通通情情况况，可可分
9、为几个工作状态：分为几个工作状态：乙类：乙类：导通角等于导通角等于180甲类：甲类：一个周期内均导通一个周期内均导通甲乙类：甲乙类：导通角大于导通角大于180丙类：丙类：导通角小于导通角小于180总之：甲类：静态损耗大，效率低，但无失真。总之：甲类：静态损耗大，效率低，但无失真。 乙类：无静态损耗（乙类：无静态损耗（ICQ=0），效率高，但失真大。），效率高，但失真大。Department of Electronics and Information Science Department of Electronics and Information Science Department of
10、Electronics and Information Science Department of Electronics and Information Science http:/http:/ 结构结构互补对称：互补对称：电路中采用两个晶体管：电路中采用两个晶体管：NPN、 PNP各一支；两管特性一致。组成各一支；两管特性一致。组成 互补对称式射极输出器互补对称式射极输出器vi-VCCT1T2vo+VCCRLiLNPN型型PNP型型5.2 乙类互补对称功率放大电路乙类互补对称功率放大电路 Department of Electronics and Information Science D
11、epartment of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 静态时：静态时：vi = 0V ic1、ic2均均=0（乙类（乙类工作状态）工作状态） vo = 0V动态时：动态时：vi 0VT1截止，截止，T2导通导通vi 0VT1导通，导通，T2截止截止iL= ic1 ;vi-VCCT1T2vo+VccRLiLiL=ic2注意：注意：
12、T1、T2两个晶体管都只在半个周期内工作。两个晶体管都只在半个周期内工作。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:/ 交越失真交越失真死区电压死区电压动画5-2Department of Electronics and
13、 Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 静态电流静态电流 ICQ、IBQ等于零；等于零；(2) 每管导通时间为半个周期每管导通时间为半个周期 ； (3) 存在交越失真。存在交越失真。 特点：特点：Department of Electronics and Informat
14、ion Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ VCES动画17-1Department of Electronics and Information Science Department of Electronics and Information Science Department of E
15、lectronics 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:/
16、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:/ Department of Electronics and Information Science Department of Electronics and Information Scienc
17、e Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 问：问：Vom=？ PT1最大最大, PT1max=？用用PT1对对Vom求导得出：求导得出：PT1max发生在发生在Vom=0.64VCC处。处。将将Vom=0.64VCC代入代入PT1表达式表达式：Department of Electronics and Information Science Department of Electronics and Info
18、rmation Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ PCM PT1max =0.2PoM23、Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science
19、Department of Electronics and Information Science http:/http:/ tvo交越失真交越失真vi t+VCC-VCCviiLRLT1T2A存在交越失真存在交越失真OCL电路电路乙类互补对称功放的缺点乙类互补对称功放的缺点Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department o
20、f Electronics and Information Science http:/http:/ 静态时静态时: T1、T2两管发射结电位分两管发射结电位分别为二极管别为二极管D1、 D2的正向导通的正向导通压降，致使两管均处于微弱导压降，致使两管均处于微弱导通状态通状态甲乙类工作状态甲乙类工作状态动态时：动态时：设设 vi 加入正弦信号。正半加入正弦信号。正半周周 T2 截止截止，T1 基极电位进一步基极电位进一步提高，进入良好的导通状态；负提高，进入良好的导通状态；负半周半周T1截止，截止，T2 基极电位进一步基极电位进一步提高，进入良好的导通状态。提高，进入良好的导通状态。+VCC-
21、VCCVLviiLRLT1T2电路中增加电路中增加 R1、D1、D2、R2支路支路1.1.基本原理基本原理 5.3 甲乙类互补对称功率放大电路甲乙类互补对称功率放大电路一一. 甲甲乙类双电源互补对称电路乙类双电源互补对称电路Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Informat
22、ion Science http:/http:/ ICQ 、IBQ 。每管导通时间大每管导通时间大于半个周期，基于半个周期，基本不失真。本不失真。 iCQvceVSC /REVSCIBQDepartment of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/h
23、ttp:/ 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:/ 电路中增加复合管电路中增加复合管增加复合管的目的：增加复合管的目的：扩大电流的驱动能力。扩大电流的驱动能力。cbeT1T2ibicbecibic 1 2晶体管的类
24、型由复合管中的第一支管子决定。晶体管的类型由复合管中的第一支管子决定。cbeT1T2ibic复合复合NPN型型复合复合PNP型型becibicDepartment 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:/ 改进后的改进后的OCL准互补准互
25、补输出功放电路：输出功放电路： T1：电压推动级（前置级）电压推动级（前置级） T2、R1、R2：UBE扩大电路扩大电路 T3、T4、T5、T6：复合管构成互补复合管构成互补对称功放对称功放准互补准互补 输出级中的输出级中的T4、T6均为均为NPN型晶体管，两者特性容易对称。型晶体管，两者特性容易对称。+VCC-VCCR1R2RLviT1T2T3T4T5T6 合理选择合理选择R1、R2大小，大小，b3、b5间间便可得到便可得到 VBE2 任意倍数的电压。任意倍数的电压。Department of Electronics and Information Science Department of
26、 Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ 单电源供电；单电源供电；. 输出加有大电容。输出加有大电容。（1）静态分析）静态分析则则 T1、T2 特性对称，特性对称，令：令：VCC/2RLuiT1T2+VCCCAVL+-UC二二. 甲甲乙类单电源互补对称电路乙类单电源互补对称电路Department of Electronics and In
27、formation Science Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ T2导通。导通。设输入端在设输入端在0.5VCC直流电平基础上加入正弦信号直流电平基础上加入正弦信号（3）输出功率及效率）输出功率及效率若忽略交越失真的影响，且若忽略交越失真的影响，且 ui 幅度足够大。则：幅度足够大。则：LCCLCCL
28、RVIVV22maxmax=，采用单电源的互补对称电路，由于每个管子的电压是原来的一采用单电源的互补对称电路，由于每个管子的电压是原来的一半（半（1/2VCC）故导出的）故导出的PO、PT、PV、PTM的公式只要将的公式只要将1/2VCC代入原来的双电源的公式中的代入原来的双电源的公式中的VCC即可。即可。（1） 静态偏置静态偏置（2）动态工作情况）动态工作情况 调整调整R1、R2阻值阻值的大小，可使的大小，可使此时电容上电压此时电容上电压此电路存在的问题：此电路存在的问题：输出电压正方向变化的幅度受到限制，达不到输出电压正方向变化的幅度受到限制，达不到VCC/2。因为。因为V i 为为负半周
29、时（负半周时（VC3为正半周为正半周b2点），点），T1导电，若导电，若T1饱和，则饱和，则VK增加增加近似为近似为VCC，但，但VBE1=VB1- VK ， VK增加增加VBE1减小使减小使IB1、IC1相应减相应减小，从而小，从而VOM=IC1RL减小使之明显小于减小使之明显小于VCC/2。2、实际电路、实际电路克服交越失真克服交越失真动画53Department of Electronics and Information Science Department of Electronics and Information Science Department of Electronics
30、 and Information Science Department of Electronics and Information Science http:/http:/ 带自举电路的单电源功放带自举电路的单电源功放静态时静态时C3充电后，其两充电后，其两端有一固定电压端有一固定电压动态时动态时由于由于C3很大，两端电压基本不变，使很大，两端电压基本不变，使D点电位随输出电压点电位随输出电压升高而升高。保证输出幅度达到升高而升高。保证输出幅度达到VCC/2。自举电路自举电路自举电路自举电路Department of Electronics and Information Science D
31、epartment of Electronics and Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ Output TransformerLessOCL: Output CapacitorLess总结：互补对称功放的类型总结：互补对称功放的类型 互补对称功放的类型互补对称功放的类型 无输出变压器形式无输出变压器形式 （ OTL电路）电路）无输出电容形式无输出电容形式 （ OC
32、L电路）电路）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:/ 实用功率放大器举例实用功率放大器举例这里介绍一个实用的这里介绍一个实用的OCL准互补功放电路。其准互补功放电路。其中主要环节有中主要环节有 ： (1) 恒流源式
33、差动放大输入级（恒流源式差动放大输入级（T1、T2、T3）；）；(2) 偏置电路（偏置电路（R1、D1、D2）；）；(3) 恒流源负载（恒流源负载（T5）；）；(4) OCL准互补功放输出级（准互补功放输出级（T7、T8、T9、 T10）；）；(5) 负反馈电路（负反馈电路（Rf、C1、Rb2构成交流电压串联负反馈）；构成交流电压串联负反馈）； (6) 共射放大级（共射放大级（T4）；）；(7) 校正环节（校正环节（C5、R4）；）；(8) UBE倍增电路（倍增电路（T6、R2、R3）；）；(9) 调整调整输出级工作点元件输出级工作点元件（Re7、Rc8、Re9、Re10）。）。将其集成起来，
34、就成为集成功放电路。将其集成起来，就成为集成功放电路。 +24VuiRLT7T8RC8-24VR2R3T6Rc1T1T2Rb1Rb2C1RfR1D1D2T3Re3T4Re4C2T5Re5C3C4T9T10Re10Re7Re9C5R4BX差动放大级差动放大级反馈级反馈级偏置电路偏置电路共射放大级共射放大级UBE倍增倍增电路电路恒流源恒流源负载负载准互补功放级准互补功放级保险管保险管负载负载实用的实用的OCL准互补功放电路：准互补功放电路：Department of Electronics and Information Science Department of Electronics and
35、Information Science Department of Electronics and Information Science Department of Electronics and Information Science http:/http:/ LM384管脚说明管脚说明:14 - 电源端（电源端（ Vcc）3、4、5、7 - 接地端（接地端（ GND）10、11、12 - 接地端（接地端（GND）2、6 - 输入端输入端 （一般（一般2脚接地）脚接地） 8 - 输出端输出端 （经（经500 电容接负载）电容接负载）)12345 678910111213141 - 接旁路电
36、容（接旁路电容（5 ）9、13 - 空脚（空脚（NC）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:/ LM384 外部电路典型接法：外部电路典型接法：500 -+ 0.1 2.7 8146215 Vccui8 调节音量调节
37、音量电源滤波电容电源滤波电容外接旁路电容外接旁路电容低通滤波低通滤波,去除高频噪声去除高频噪声输入信号输入信号输出耦合大电容输出耦合大电容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:/ 5.3.2 5.3.4n第五版：第五版：P407 8.3.2 8.4.4
