压控函数发生器课程设计报告修订版

电子技术课程设计（模电）专业____________班级____________姓名____________二○一二年十月压控函数发生器的设计目录一、课程设计内容及方框图···········································································································21、课程设计内容·····················································································································22、方框图·································································································································2二、方案选择···································································································································2三、框图工作原理···························································································································3（一）各框内电路独立设计···································································································3（二）方波-三角波：···········································································································10四、仿真调试·································································································································12（一）仿真过程·····················································································································121、方波-三角波·······························································································122、三角波-正弦波·······································································································14（二）实验过程·····················································································································151、方波-三角波·············································································································152、三角波-正弦波·······································································································17五、参考文献·································································································································18附件一：器件表·····························································································································19附件二：总图·································································································································192压控函数发生器一、课程设计内容及方框图1、课程设计内容设计一个压控函数发生器，可以产生方波、正弦波和三角波。要求：（1）输入信号：V100的直流电压（2）输出信号：三角波电压为4V；正弦波为2V；方波为010V（3）输出信号频率：0-10KHz；频率转换误差小于30Hz2、方框图ixVa输出4V三角波b输出010V方波C输出正弦波为2V二、方案选择函数发生器能自动产生正弦波、三角波、方波及锯齿波、阶梯波等电压波形，其电路中使用的器件可以是分立器件，也可以是集成电路，本课程设计主要研究由集成运算放大器与晶体管差分放大器组成的方波--三角波—正弦波函数发生器的设计方法。产生正弦波、方波、三角波的方案有多种，如正弦波震荡-----对称波形------三角波对称波形-----三角波-----正弦波三角波-----正弦波-----对称波形本课程设计中，采用先产生方波—三角波，再将三角波变成正弦波的电路设计方法。由积分器和反馈比较器分别得到三角波、方波，再将三角波输入差分放大器，利用差分放大器传输曲线的非线性特征得到正弦波。跟随器极性变换积分电路施密特比较反馈非线性转换器abc3三、框图工作原理（一）各框内电路独立设计1、ixV的产生由于实验室提供的电源电压为V12，对ixV的要求为V100的直流电压，故采用可变电阻电位分压方式产生，具体发生电路如图13。因为电源电压为12V，故R15R2，在此选取kR11，kR52。图132、跟随器：在同相比例运算电路中，将输入电压的全部反馈到反相输入端，从而使输入电压值等于输出电压值（方向相反），即形成电压跟随器，理想运放的开环增益为无穷大，因而电压跟随器有较好的跟随特性。（图23）图323端出入直流电压，1端输出跟随电压，4端接-12V，8端接+12V3、极性变换：当开关闭合时，UiR3U0R4，且为保证电路对称，R3//R4=R6。4当开关打开时，Ui=U0。则为了满足电路的极性变换要求，R3=R4，且R3//R4=R6=R5。根据以上要求：本课程设计中选取R3=R4=10K，R5=R6=5K。见图33。图33s9013不导通时，开关断开S9013导通时，开关闭合4、积分器：积分运算电路中，由于集成运放的同相输入端通过9R接地，pNUU0，为“虚地”。电路中，电容C1中电流等于电阻R7中电流，incRUiiR7，输出电压与电容上电压的关系为occUU，而电容上电压等于其电流的积分，故：21ocinoc1711UUdtU()tttRC（式3-4-1）iU0U5当in12Utt在为常量，ocin21oc1711UU()U()tttRC（式3-4-2）当输入信号为方波时，输出信号为三角波。图341根据以上分析，同时满足设计要求（输出三角波峰峰值为8V，频率为010KHz），令f10KHz，fT1由（式3-4-2）得：442*10*171)2(TCRTUoc71RC510*25.6（式3-4-3）实验室里有nFC101，故得kR25.67。图3-4-2C2的作用为相位反馈，有轻微的波形变形5、施密特比较反馈：T2T1010446图3-5如图35所示施密特电路将输入的三角波转换成方波输出，同时利用三极管的开关特性控制机型变化中的开关。具体原理如下：根据施密特电路的工作原理得：运算放大器U4A的输出电压在正、负饱和之间转换，即：satV0V。输出电压由11,10RR反馈到正相输入端V=V0，其中反馈因数111010RRR。输入三角波iU的峰峰值为8V，即得到反馈的上下临界电压分别为：4111010satTHVRRRV4111010satTLVRRRV（见图3-5-1）运算放大器工作电压satV为12V，412*111010RRR，得21011RR但在考虑管压降以及本课程设计的具体要求，实际试验中21011RR。图3-5-1然后V0再经过二极管D1，由于二极管单向导通的特性，便可得到要求中三角波0U0iUiU7010V的方波。6、非线性转换器：（一）三角波-正弦波图3-6-1在三角波-正弦波的转换过程中，选用了差分放大器作为转换电路。波形变换的原理是：利用差分对管的饱和与截止特性进行变换。差分放大器的传输特性曲线：idT0CEvvIii1e，（式3-6-1）式中：EI1cI，0I为差分放大器的恒定电流；TV为温度的电压常量，当室温为25C时，TV26mV。输入idV为峰峰值为8V的三角波，设表达式为：)43(16)4(16TtTtTTVid（式3-6-2）式中：T为三角波的周期。iU三角波0U正弦波TtT2（）Tt2（0）8代入差分放大器的传输特性曲线，则：)43(160)4(16011)(TtTtTTceIeIti361（见图）361图为了使输出波形更接近正弦波，要求：44T2TTt2（0）TtT2（）363（式）9（1）传输特性曲线尽可能对称，线性区尽可能窄；（2）三极管尽可能工作在非线性区，则应使放大器的放大倍数尽可能大，设置较低的静态工作点，同时输入较小的信号。6.1恒流源电路设计方案一根据要求三极管尽可能工作在低静态工作点，实验要求0I近似等于0.3mA由于管压降，R16两端电压为0.3V，即R17分压得到电压为1V，实验提供滑动变阻器R18=10KΩ方案二镜像电流源13150RRRUUIBEODD，R2=R5=20k，R1=10k，R13实际电路中选取总阻值为10k的电位器。图362为电流源方案一下的三角波-正弦波的变换电路，其中21R调节三角波的输入幅度，18R调节电路的对称性，5,4CC为极性电容。ce0Ic0I10图362（二）方波-三角波：图37为方波-三角波转换电路,a端输出V10的方波，b端输出0-10V的方波，c端输出V4的三角波。iU三角波11图3-7根据以上对个独立框图电路的设计，由电阻电位分压方式产生的ixV，经电压跟随器和极性转换器，并在U5的控制下，在a点形成了-10~10V的方波，经过积分电路，在c端输出三角波，三角波经过施密特电路在b点输出方波，由于二极管的单向导通特性，输出方波b只有Y轴上方的图像。其中，当ixV-10~10V在变化的过程中，输出信号频率从010kHz变化。由ocin21oc1711UU()U()tttRC（式3-4-2）得：442**171)2(TUCRTUocix（式3-7-1）ix71UT16RC（式3