正弦波方波三角波发生电路.docx
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正弦波方波三角波发生电路
正弦波、方波、三角波发生电路
一、设计目的及要求:
1.1、设计目的:
掌握波形产生电路的设计、组装和调试的方法;
(1).
(2).熟悉集成电路:
集成运算放大器LM324,并掌握其工作原理。
1.2、设计要求:
(1)设计波形产生电路。
(2)信号频率范围:
100Hz——1000Hz。
(3)信号波形:
正弦波。
二、实验方案:
方案一:
为了产生正弦波,必须在放大电路里加入正反馈,因此放大电路和正反馈网络是振荡电路的最主要部分。
但是,这样两部分构成的振荡器一般得不到正弦波,这是由于很难控制正反馈的量。
如果正反馈量大,则增幅,输出幅度越来越大,最后由三极管的非线性限幅,这必然产生非线性失真。
反之,如果正反馈量不足,则减幅,可能停振,为此振荡电路要有一个稳幅电路。
为了获得单一频率的正弦波输出,应该有选频网络,选频网络往往和正反馈网络或放大电路合而为一。
选频网络由R、C和L、C等电抗性元件组成。
正弦波振荡器的名称一般由选频网络来命名。
正弦波发生电路的组成:
放大电路、正反馈网络、选频网络、稳幅电路。
产生正弦波的条件与负反馈放大电路产生自激的条件十分类似。
只不过负反馈放大电路中是由于信号频率达到了通频带的两端,产生了足够的附加相移,从而使负反馈变成了正反馈。
在振荡电路中加的就是正反馈,振荡建立后只是一种频率的信号,无所谓附加相移。
(a)负反馈放大电路(b)正反馈振荡电路
图1振荡器的方框图
比较图1(a)和(b)就可以明显地看出负反馈放大电路和正反馈振荡电路的区别了。
由于
,,,,振荡电路的输入信号=0,所以=。
由于正、负号的改变,正反馈的放大倍数为:
XXXiif
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,.A,,,式中是放大电路的放大倍数,F是反馈网络的放大倍数。
A,Af,,1,AF
..
振荡条件:
AF,1
..
幅度平衡条件:
,=1AF
相位平衡条件:
=,+,=,2n,AFAF
..
振荡器在刚刚起振时,为了克服电路中的损耗,需要正反馈强一些,即要求|AF|,1
..
这称为起振条件。
既然,起振后就要产生增幅振荡,需要靠三极管大信号运用时|AF|,1
的非线性特性去限制幅度的增加,这样电路必然产生失真。
这就要靠选频网络的作用,选出失真波形的基波分量作为输出信号,以获得正弦波输出。
也可以在反馈网络中加入非线性稳幅环节,用以调节放大电路的增益,从而达到稳幅的目的。
方案二:
电压比较器RC充放电反馈回路
占空比可调积分电路
锯齿波矩形波方波
积
分低频滤波电正弦波路三角波
比例放大电路,得到需要幅值;峰峰
值的信号波
图2方波、三角波、正弦波、锯齿波信号发生器的原理框图
该发生器通过将滞回电压比较器的输出信号通过RC电路反馈到输入端,即可组成矩形波信号发生器。
然后经过积分电路产生三角波,通过改变方波的占空比不仅可以得到锯齿波,还可得到额外的矩形波。
三角波通过低通滤波电路来实现正弦波的输出。
然后将各种信号通过比例放大电路得到需要幅值;峰峰值的信号波
该电路具有结构、思路简单,运行时性能稳定且能较好的符合设计要求,对原器件要求不高,且成本低廉、调整方便。
thethree.Third,seriouslyimplementtheCentral,provincial,municipalandCountypartyCommitteeontheestablishmentofasoundworkstyleconstructionviewsofthelong-actingmechanismandontheimplementationofthethreeSunscallsforfurtherstrengtheningofeducationadministrationandsupervisionofpartymembersandcadres,fromthe...Acceptsupervisionandearnestlygrasp,balance,twopromotion,importantjobhimself,theSecretaryofdevelopment,majorissuespersonally.5.stronglysupportsaccountabilitydisciplinediscipline.Administrativeprovisionsonstrictenforcementofpartymembersandcadrestoaskallthedisciplineinspectionandsupervisioncadresinaccordancewiththeironitselfmustbeahardrequirement,adheretotheresponsibilitiesandplay,earnestlyfulfilltheirdutiesofsupervisionandaccountabilityforZhiJI.ZhenintofullplayandtheoversightroleoftheCommission,establishandimprovethevillagerulesandcommunityconventions,promotingjointpublicandservingthesunshinepubliclyavailableimplementationoftheplatformforaction.Disciplineinhandlingcases,adheretofindalongwithscrutiny,toappointtheinterferenceandresistance,backedbycourageous,findtheproblemcorrected,powerfulmaintenancetheseriousnessofresponsibilityofuncorrupted.ActivelypromotethedisciplineCommitteedetailedswitchand,casting,tree-generatingactivities.Promote
为更好理解两种电路的结构及原理,本文采用方案一产生正弦波,方案二产生方波和三
角波。
三、设计步骤:
3.1、RC正弦波振荡电路
RC串并联网络的电路如图3所示。
RC串联臂的阻抗用Z表示,RC并联臂的1
图3RC串并联网络阻抗用Z表示。
其频率响应如下2
R2,,Z,R,(1/jC)Z,R//(1/jC),1112221,jRC,22
.,.VZR/(1,jRC)f2222F,,,,,.Z,ZR,(1/jC)+[R/(1,jRC)]1211222Vo
R2,,,[R,(1/jC)](1,jRC),R11222
R2,,,R,(1/jC)+jRRC,RC/C,R111222212
1,RC112,(1,,),j(,)RC12RC,RC2121
谐振频率为
1f=02πRRCC1212
当R=R,C=C时,谐振角频率和谐振频率分别为:
1212
11f,,,,00RC2,RC
幅频特性
.11F,,,,RC12222120,RC(1,,),(,)3,(,)12RCRC,,,21210相频特性
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,,10,,RC,12,,,RC021arctgarctg,,,,,FRC3121,,RC21
.1当f=f时的反馈系数,且与频率f的大小无关,此时的相角=0:
。
即调节,F,00F3
谐振频率不会影响反馈系数和相角,在调节频率的过程中,不会停振,也不会使输出幅度改变。
3.2、基本文氏桥振荡电路
RC文氏桥振荡器的电路如图4所示,RC串并联网络是正反馈网络,另外还增加了R3和R负反馈网络。
4
图4RC文氏桥振荡器
CR和CR正反馈支路与RR负反馈支路正好构成一个桥路,称为文氏桥。
当C、、、1122341=C、R=R时212
..V1fF,,.3Vo
,=0:
F
1f=02πRC
..
为满足振荡的幅度条件,,=1,所以A?
3。
加入RR支路,构成串联电压负反馈AFf34
R3A,1,,3fR4
f0由于A,3。
这时正反馈超过了负反馈,说明频率为的扰动会被再生的放大,导致f
整个电路进入一个幅度不断增长的振荡过程中。
此时电路是不稳定的。
如下图所示
thethree.Third,seriouslyimplementtheCentral,provincial,municipalandCountypartyCommitteeontheestablishmentofasoundworkstyleconstructionviewsofthelong-actingmechanismandontheimplementationofthethreeSunscallsforfurtherstrengtheningofeducationadministrationandsupervisionofpartymembersandcadres,fromthe...Acceptsupervisionandearnestlygrasp,balance,twopromotion,importantjobhimself,theSecretaryofdevelopment,majorissuespersonally.5.stronglysupportsaccountabilitydisciplinediscipline.Administrativeprovisionsonstrictenforcementofpartymembersandcadrestoaskallthedisciplineinspectionandsupervisioncadresinaccordancewiththeironitselfmustbeahardrequirement,adheretotheresponsibilitiesandplay,earnestlyfulfilltheirdutiesofsupervisionandaccountabilityforZhiJI.ZhenintofullplayandtheoversightroleoftheCommission,establishandimprovethevillagerulesandcommunityconventions,promotingjointpublicandservingthesunshinepubliclyavailableimplementationoftheplatformforaction.Disciplineinhandlingcases,adheretofindalongwithscrutiny,toappointtheinterferenceandresistance,backedbycourageous,findtheproblemcorrected,powerfulmaintenancetheseriousnessofresponsibilityofuncorrupted.ActivelypromotethedisciplineCommitteedetailedswitchand,casting,tree-generatingactivities.Promote
图5>3时产生波形Af
3.2参数设计及运算
3.2.1器件选择
集成运算放大器(LM324),二极管(1N4934),示波器(XSC1),固定电容(1nF),可变电容
(0,9nF),及各种型号电阻。
3.2.2参数计算
1R,158K,f0,根据稳定振荡条件:
在选频网络中,选择,根据频率的变化范围2,RC
100Hz,1000Hz计算可变电容器C值如下;
1f100,,100HZ,max2RC
1Cmax,,10nF,2,158,100000
1,100HZ,max2,158,1000,C
同理,
1f,,1000HZ1000,2RCmin
1,1000HZ3,2,158,10,Cmin
1C,,1nFmin6,2,158,10
1nF0nF,9nF所以选择可变电容器的范围在之间变化,与电容并联,总电容在1nF~10nF内变化,而且保持两个可变电容同时变化。
thethree.Third,seriouslyimplementtheCentral,provincial,municipalandCountypartyCommitteeontheestablishmentofasoundworkstyleconstructionviewsofthelong-actingmechanismandontheimplementationofthethreeSunscallsforfurtherstrengtheningofeducationadministrationandsupervisionofpartymembersandcadres,fromthe...Acceptsupervisionandearnestlygrasp,balance,twopromotion,importantjobhimself,theSecretaryofdevelopment,majorissuespersonally.5.stronglysupportsaccountabilitydisciplinediscipline.Administrativeprovisionsonstrictenforcementofpartymembersandcadrestoaskallthedisciplineinspectionandsupervisioncadresinaccordancewiththeironitselfmustbeahardrequirement,adheretotheresponsibilitiesandplay,earnestlyfulfilltheirdutiesofsupervisionandaccountabilityforZhiJI.ZhenintofullplayandtheoversightroleoftheCommission,establishandimprovethevillagerulesandcommunityconventions,promotingjointpublicandservingthesunshinepubliclyavailableimplementationoftheplatformforaction.Disciplineinhandlingcases,adheretofindalongwithscrutiny,toappointtheinterferenceandresistance,backedbycourageous,