函数信号发生器(毕业设计)

陕西国防学院电子工程系毕业论文1摘要本系统以ICL8038集成块为核心器件，制作一种函数信号发生器，制作成本较低。适合学生学习电子技术测量使用。ICL8038是一种具有多种波形输出的精密振荡集成电路，只需要个别的外部元件就能产生从0.001Hz～30KHz的低失真正弦波、三角波、矩形波等脉冲信号。输出波形的频率和占空比还可以由电流或电阻控制。另外由于该芯片具有调制信号输入端，所以可以用来对低频信号进行频率调制。函数信号发生器根据用途不同，有产生三种或多种波形的函数发生器，其电路中使用的器件可以是分离器件，也可以是集成器件，产生方波、正弦波、三角波的方案有多种，如先产生正弦波，根据周期性的非正弦波与正弦波所呈的某种确定的函数关系，再通过整形电路将正弦波转化为方波，经过积分电路后将其变为三角波。也可以先产生三角波-方波，再将三角波或方波转化为正弦波。随着电子技术的快速发展，新材料新器件层出不穷，开发新款式函数信号发生器，器件的可选择性大幅增加，例如ICL8038就是一种技术上很成熟的可以产生正弦波、方波、三角波的主芯片。所以，可选择的方案多种多样，技术上是可行的。关键词：ICL8038，波形，原理图，常用接法陕西国防学院电子工程系毕业论文2目录摘要·······································································1目录·····································································2第一章项目任务·························································31.1项目建·····························································31.2项目可行性研究·······················································3第二章方案选择··························································42.1[方案一]···························································42.2[方案二]···························································4第三章基本原理··························································53.1函数发生器的组成····················································63.2方波发生器························································63.3三角波发生器······················································73.4正弦波发生器······················································9第四章稳压电源························································104.1直流稳压电源设计思路·············································104.2直流稳压电源原理·················································114.3设计方法简介······················································12第五章振荡电路························································155.1RC振荡器的设计··················································15第六章功率放大器·························································176.1OTL功率放大器··················································17第七章系统工作原理与分析·················································197.1ICL8038芯片简介··················································197.2ICL8038的应用··················································197.3ICL8038原理简介··················································197.4电路分析··························································207.5工作原理························································207.6正弦函数信号的失真度调节··········································237.7ICL8038的典型应用··············································24致谢·····································································25心得体会··································································26参考文献··································································27附录1·····································································28附录2·····································································29附录3·····································································30陕西国防学院电子工程系毕业论文3第一章项目任务1.1项目建议函数信号发生器是工业生产、产品开发、科学研究等领域必备的工具，它产生的锯齿波和正弦波、矩形波、三角波是常用的基本测试信号。在示波器、电视机等仪器中，为了使电子按照一定规律运动，以利用荧光屏显示图像，常用到锯齿波信号产生器作为时基电路。例如，要在示波器荧光屏上不失真地观察到被测信号波形，要求在水平偏转线圈上加随时间线性变化的电压——锯齿波电压，使电子束沿水平方向匀速搜索荧光屏。对于三角波，方波同样有重要的作用，而函数信号发生器是指一般能自动产生方波正弦波三角波以及锯齿波阶梯波等电压波形的电路或仪器。因此，建议开发一种能产生方波、正弦波、三角波的函数信号发生器。1.2项目可行性研究函数信号发生器根据用途不同，有产生三种或多种波形的函数发生器，其电路中使用的器件可以是分离器件，也可以是集成器件，产生方波、正弦波、三角波的方案有多种，如先产生正弦波，根据周期性的非正弦波与正弦波所呈的某种确定的函数关系，再通过整形电路将正弦波转化为方波，经过积分电路后将其变为三角波。也可以先产生三角波-方波，再将三角波或方波转化为正弦波。随着电子技术的快速发展，新材料新器件层出不穷，开发新款式函数信号发生器，器件的可选择性大幅增加，例如ICL8038就是一种技术上很成熟的可以产生正弦波、方波、三角波的主芯片。所以，可选择的方案多种多样，技术上是可行的。陕西国防学院电子工程系毕业论文4第二章方案选择2.1〖方案一〗由文氏电桥产生正弦振荡，然后通过比较器得到方波，方波积分可得三角波。这一方案为一开环电路，结构简单，产生的正弦波和方波的波形失真较小①。但是对于三角波的产生则有一定的麻烦，因为题目要求有1000倍的频率覆盖系数，显然对于1000倍的频率变化会有积分时间dt的1000倍变化从而导致输出电压振幅的1000倍变化。而这是电路所不希望的。幅度稳定性难以达到要求。而且通过仿真实验会发现积分器极易产生失调。②2.2〖方案二〗利用ICL8038芯片构成8038集成函数发生器。8038集成函数发生器是一种多用途的波形发生器，可以用来产生正弦波、方波、三角波和锯齿波，其振荡频率可通过外加的直流电压进行调节，所以是压控集成信号产生器。由于外接电容C的充、放电电流由两个电流源控制，所以电容C两端电压uc的变化与时间成线形关系，从而可以获得理想的三角波输出。8038电路中含有正弦波变换器，故可以直接将三角波变成正弦波输出。另外还可以将三角波通过触发器变成方波输出。该方案的特点是十分明显的：⑴线性良好、稳定性好；⑵频率易调，在几个数量级的频带范围内，可以方便地连续地改变频率，而且频率改变时，幅度恒定不变；⑶不存在如文氏电桥那样的过渡过程，接通电源后会立即产生稳定的波形；⑷三角波和方波在半周期内是时间的线性函数，易于变换其他波形。综合上述分析，我们采用了第二种方案来产生信号。陕西国防学院电子工程系毕业论文5第三章基本原理3.1函数发生器的组成函数发生器一般是指能自动产生正弦波、方波、三角波的电压波形的电路或者仪器。电路形式可以采用由运放及分离元件构成；也可以采用单片集成函数发生器。根据用途不同，有产生三种或多种波形的函数发生器，本课题介绍方波、三角波、正弦波函数发生器的方法。函数信号发生器是是由基础的非正弦信号发生电路和正弦波形发生电路组合而成。下面我们将分别对各个波形的发生进行分析，从而达到在合成电路时使电路更加合理。3.2方波发生器：如图3-2-1用运算放大器滞回比较器和fR、C积分电路组成的，输出电压经fR、C反馈到运放的反相输出端，因此积分电路起延迟和负反馈作用。图3-2-1参看图3-2-1所示电路，设在接通电源的时刻，电容器两端电压0Cu，输出电压ZOUu，则加到运放同相输出端的电压为ZZPFUURRRu212。式中，)(212RRRF。此时ZOUu通过1R向C充电，使运放反相输入电压CNuu由零逐渐上升。在PNuu以前，ZOUu保持不变。在1tt时刻，Nu上升到略高于Pu，Ou由高电平跳到低电平，即变为ZU。ZOUu时，ZPFUu，同时ZOUu通过fR向C充电，使运放反相输入端电压CNuu由零逐渐上升。在PNuu以前，ZOUu保持不变。在2tt时刻，Nu下降到略低于Pu，Ou由低电平跳到高电平，即变为ZU，又回到原始状态。如此周而复始，循环不已，因此产生振荡，输出方波。根据上边的分析，可以画出Cu与Ou的波形如下图所示：陕西国防学院电子工程系毕业论文6图3-2-2由波形可知，Cu从1t时刻的ZZZFURRUR)(21下降到2t时刻的ZFU，再上升到3t时刻的ZFU，所需的时间就是一个振荡周期OT在1t到2t这段时间，Cu的变化规律是简单RC电路充放电规律，其常数为CRf，初始值为ZFU（1t时刻），终了值为ZU（t→∞），故CRttZZZCfeUFUUu/)(1)]([在2tt时，ZCFUu，代入上式后可求得)21ln(11ln1212RRCRFFCRttff同样可求得)21ln(121