<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta charset="utf-8">
<meta name="generator" content="pdf2htmlEX">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
<link rel="stylesheet" href="https://static.pudn.com/base/css/base.min.css">
<link rel="stylesheet" href="https://static.pudn.com/base/css/fancy.min.css">
<link rel="stylesheet" href="https://static.pudn.com/prod/directory_preview_static/624f05916caf596192b82381/raw.css">
<script src="https://static.pudn.com/base/js/compatibility.min.js"></script>
<script src="https://static.pudn.com/base/js/pdf2htmlEX.min.js"></script>
<script>
try{
pdf2htmlEX.defaultViewer = new pdf2htmlEX.Viewer({});
}catch(e){}
</script>
<title></title>
</head>
<body>
<div id="sidebar" style="display: none">
<div id="outline">
</div>
</div>
<div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/624f05916caf596192b82381/bg1.jpg"><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">NE555</div><div class="t m0 x1 h2 y2 ff1 fs0 fc0 sc0 ls0 ws0">NE555</div><div class="t m0 x1 h2 y3 ff1 fs0 fc0 sc0 ls0 ws0">NE555</div><div class="t m0 x1 h3 y1 ff1 fs0 fc0 sc0 ls0 ws0">NE555<span class="_ _0"> </span><span class="ff2 sc1">中文资料详<span class="_ _1"></span>解</span></div><div class="t m0 x2 h4 y4 ff3 fs1 fc1 sc0 ls0 ws0">555<span class="_ _2"> </span><span class="ff2">芯片引脚图<span class="_ _1"></span>及引脚描述</span></div><div class="t m0 x3 h4 y5 ff3 fs1 fc1 sc0 ls0 ws0">555<span class="_ _2"> </span><span class="ff2">的<span class="_ _3"> </span></span>8<span class="_ _4"> </span><span class="ff2">脚是集成电<span class="_ _1"></span>路工作电压输<span class="_ _1"></span>入端<span class="_ _5"> </span>,<span class="_ _6"> </span>电压为<span class="_ _7"> </span><span class="ff3">5<span class="_ _8"> </span></span>~<span class="_ _9"> </span><span class="ff3">18V<span class="_ _a"> </span></span>,<span class="_ _6"> </span>以<span class="_ _3"> </span><span class="ff3">UCC<span class="_ _b"> </span></span>表示<span class="_ _c"> </span>;<span class="_ _6"> </span>从分压<span class="_ _1"></span>器上看</span></div><div class="t m0 x2 h4 y6 ff2 fs1 fc1 sc0 ls0 ws0">出<span class="_ _9"> </span>,<span class="_ _d"> </span>上比较器<span class="_ _e"> </span><span class="ff3">6<span class="_ _4"> </span></span>脚<span class="_ _3"> </span><span class="ff3">A1<span class="_ _f"> </span></span>的5脚接在<span class="_ _10"> </span><span class="ff3">R1<span class="_ _11"> </span></span>和<span class="_ _3"> </span><span class="ff3">R2<span class="_ _11"> </span></span>之间<span class="_ _c"> </span>,<span class="_ _d"> </span>所以<span class="_ _12"> </span><span class="ff3">5<span class="_ _4"> </span></span>脚的电压固定在<span class="_ _13"> </span><span class="ff3">2UCC/3<span class="_ _14"> </span></span>上<span class="_ _9"> </span>;<span class="_ _d"> </span>下比</div><div class="t m0 x2 h4 y7 ff2 fs1 fc1 sc0 ls0 ws0">较器<span class="_ _12"> </span><span class="ff3">A2<span class="_ _f"> </span></span>接在<span class="_ _12"> </span><span class="ff3">R2<span class="_ _11"> </span></span>与<span class="_ _3"> </span><span class="ff3">R3<span class="_ _11"> </span></span>之间,<span class="_ _15"> </span><span class="ff3">A2<span class="_ _f"> </span></span>的同相输入<span class="_ _1"></span>端电位被固定<span class="_ _1"></span>在<span class="_ _16"> </span><span class="ff3">UCC/3<span class="_ _17"> </span></span>上。</div><div class="t m0 x2 h5 y8 ff1 fs1 fc1 sc0 ls0 ws0">NE555</div><div class="t m0 x2 h5 y9 ff1 fs1 fc1 sc0 ls0 ws0">NE555</div><div class="t m0 x2 h5 ya ff1 fs1 fc1 sc0 ls0 ws0">NE555</div><div class="t m0 x2 h4 y8 ff1 fs1 fc1 sc0 ls0 ws0">NE555<span class="_ _18"> </span><span class="ff2 sc2">管脚功能介<span class="_ _1"></span>绍:</span></div><div class="t m0 x3 h4 yb ff3 fs1 fc1 sc0 ls0 ws0">1<span class="_ _4"> </span><span class="ff2">脚为地。<span class="_ _19"> </span></span>2<span class="_ _4"> </span><span class="ff2">脚为触发输<span class="_ _1"></span>入端;<span class="_ _1a"> </span><span class="ff3">3<span class="_ _4"> </span></span>脚为输出<span class="_ _1"></span>端,输<span class="_ _1"></span>出的电<span class="_ _1"></span>平状态<span class="_ _1"></span>受触发<span class="_ _1"></span>器控制<span class="_ _1"></span>,而触<span class="_ _1"></span>发</span></div><div class="t m0 x2 h4 yc ff2 fs1 fc1 sc0 ls0 ws0">器受上比较<span class="_ _1"></span>器<span class="_ _1b"> </span><span class="ff3">6<span class="_ _4"> </span></span>脚和下比较器<span class="_ _1c"> </span><span class="ff3">2<span class="_ _4"> </span></span>脚的控制。</div><div class="t m0 x3 h4 yd ff2 fs1 fc1 sc0 ls0 ws0">当触发器接<span class="_ _1"></span>受上比较器<span class="_ _1d"> </span><span class="ff3">A1<span class="_ _f"> </span></span>从<span class="_ _3"> </span><span class="ff3">R<span class="_ _1e"> </span></span>脚输入的高<span class="_ _1"></span>电平时<span class="_ _1f"> </span>,<span class="_ _6"> </span>触发器被置于复位状<span class="_ _1"></span>态<span class="_ _20"> </span>,<span class="_ _6"> </span><span class="ff3">3<span class="_ _4"> </span></span>脚输出</div><div class="t m0 x2 h4 ye ff2 fs1 fc1 sc0 ls0 ws0">低电平;</div><div class="t m0 x3 h4 yf ff3 fs1 fc1 sc0 ls0 ws0">2<span class="_ _4"> </span><span class="ff2">脚<span class="_ _9"> </span>和<span class="_ _3"> </span></span>6<span class="_ _21"> </span><span class="ff2">脚是互补的<span class="_ _22"> </span>,<span class="_ _23"> </span></span>2<span class="_ _4"> </span><span class="ff2">脚只对低电<span class="_ _1"></span>平起作用<span class="_ _24"> </span>,<span class="_ _23"> </span>高电平对它不起<span class="_ _1"></span>作用<span class="_ _24"> </span>,<span class="_ _23"> </span>即电压小<span class="_ _19"> </span>于<span class="_ _25"> </span><span class="ff3">1Ucc/3</span></span></div><div class="t m1 x4 h4 yf ff2 fs1 fc1 sc0 ls0 ws0">,</div><div class="t m0 x2 h4 y10 ff2 fs1 fc1 sc0 ls0 ws0">此时<span class="_ _12"> </span><span class="ff3">3<span class="_ _4"> </span></span>脚输出高电平<span class="_ _26"> </span>。<span class="_ _27"> </span><span class="ff3">6<span class="_ _4"> </span></span>脚为阈值端<span class="_ _22"> </span>,<span class="_ _27"> </span>只对高<span class="_ _1"></span>电平起作用<span class="_ _1f"> </span>,<span class="_ _27"> </span>低电平<span class="_ _1"></span>对它不起作用<span class="_ _24"> </span>,<span class="_ _27"> </span>即<span class="_ _1"></span>输入<span class="_ _28"> </span>电</div><div class="t m0 x2 h4 y11 ff2 fs1 fc1 sc0 ls0 ws0">压大<span class="_ _1"></span>于<span class="_ _29"> </span><span class="ff3">2<span class="_ _4"> </span>Ucc/3<span class="_ _2a"> </span></span>,称<span class="_ _1"></span>高触发<span class="_ _1"></span>端,<span class="_ _2b"> </span><span class="ff3">3<span class="_ _4"> </span></span>脚输出低<span class="_ _1"></span>电平,<span class="_ _1"></span>但有一<span class="_ _1"></span>个先决<span class="_ _1"></span>条件,<span class="_ _1"></span>即<span class="_ _2c"> </span><span class="ff3">2<span class="_ _4"> </span></span>脚电位必<span class="_ _1"></span>须大<span class="_ _2d"> </span>于</div><div class="t m0 x2 h4 y12 ff3 fs1 fc1 sc0 ls0 ws0">1Ucc/3<span class="_ _15"> </span><span class="ff2">时才有效。<span class="_ _22"> </span></span>3<span class="_ _2e"> </span><span class="ff2">脚在高电位<span class="_ _1"></span>接近电源电压<span class="_ _2f"> </span><span class="ff3">Ucc<span class="_ _30"> </span></span>,输出电流<span class="_ _1"></span>最大可打<span class="_ _31"> </span><span class="ff3">200mA<span class="_ _15"> </span></span>。</span></div><div class="t m0 x3 h4 y13 ff3 fs1 fc1 sc0 ls0 ws0">4<span class="_ _4"> </span><span class="ff2">脚是复位端<span class="_ _22"> </span>,<span class="_ _6"> </span>当<span class="_ _3"> </span></span>4<span class="_ _4"> </span><span class="ff2">脚电位小于<span class="_ _10"> </span></span>0.4V<span class="_ _32"> </span><span class="ff2">时<span class="_ _9"> </span>,<span class="_ _9"> </span>不<span class="_ _1"></span>管<span class="_ _12"> </span><span class="ff3">2<span class="_ _8"> </span></span>、<span class="_ _9"> </span><span class="ff3">6<span class="_ _21"> </span></span>脚状态如何<span class="_ _22"> </span>,<span class="_ _9"> </span>输出端<span class="_ _7"> </span><span class="ff3">3<span class="_ _4"> </span></span>脚都输出低</span></div><div class="t m0 x2 h4 y14 ff2 fs1 fc1 sc0 ls0 ws0">电平。</div><div class="t m0 x3 h4 y15 ff3 fs1 fc1 sc0 ls0 ws0">5<span class="_ _4"> </span><span class="ff2">脚是控制端<span class="_ _1"></span>。</span></div><div class="t m0 x3 h4 y16 ff3 fs1 fc1 sc0 ls0 ws0">7<span class="_ _4"> </span><span class="ff2">脚称放电端<span class="_ _22"> </span>,<span class="_ _6"> </span>与<span class="_ _3"> </span></span>3<span class="_ _4"> </span><span class="ff2">脚输出同步<span class="_ _22"> </span>,<span class="_ _9"> </span>输<span class="_ _1"></span>出电平一致<span class="_ _26"> </span>,<span class="_ _6"> </span>但<span class="_ _3"> </span><span class="ff3">7<span class="_ _4"> </span></span>脚并不输出电流<span class="_ _33"> </span>,<span class="_ _6"> </span>所以<span class="_ _12"> </span><span class="ff3">3<span class="_ _4"> </span></span>脚称为</span></div><div class="t m0 x2 h4 y17 ff2 fs1 fc1 sc0 ls0 ws0">实高(或低<span class="_ _22"> </span>)<span class="_ _23"> </span>、<span class="_ _9"> </span><span class="ff3">7<span class="_ _4"> </span></span>脚称为虚高。</div><div class="t m0 x3 h4 y18 ff3 fs1 fc1 sc0 ls0 ws0">1<span class="_ _9"> </span>555<span class="_ _2"> </span><span class="ff2">集成电路的<span class="_ _1"></span>框图及工作原<span class="_ _1"></span>理</span></div><div class="t m0 x5 h4 y19 ff3 fs1 fc1 sc0 ls0 ws0">555<span class="_ _2"> </span><span class="ff2">集成电路开<span class="_ _1"></span>始是作定时器<span class="_ _1"></span>应用的<span class="_ _34"> </span>,<span class="_ _d"> </span>所以叫做<span class="_ _e"> </span><span class="ff3">555<span class="_ _2"> </span></span>定时器或<span class="_ _e"> </span><span class="ff3">555<span class="_ _2"> </span></span>时基电路<span class="_ _35"> </span>。<span class="_ _d"> </span>但后</span></div><div class="t m0 x2 h4 y1a ff2 fs1 fc1 sc0 ls0 ws0">来经过开发<span class="_ _22"> </span>,<span class="_ _d"> </span>它除了作定时延<span class="_ _1"></span>时控制外<span class="_ _36"> </span>,<span class="_ _d"> </span>还可用于调光<span class="_ _26"> </span>、<span class="_ _d"> </span>调温<span class="_ _c"> </span>、<span class="_ _6"> </span>调压<span class="_ _c"> </span>、<span class="_ _d"> </span>调速等多种控制<span class="_ _1"></span>及计</div><div class="t m0 x2 h4 y1b ff2 fs1 fc1 sc0 ls0 ws0">量检测<span class="_ _15"> </span>。<span class="_ _d"> </span>此外<span class="_ _c"> </span>,<span class="_ _6"> </span>还可以组成脉冲振荡<span class="_ _24"> </span>、<span class="_ _d"> </span>单稳<span class="_ _c"> </span>、<span class="_ _6"> </span>双稳和脉冲<span class="_ _1"></span>调制电路<span class="_ _24"> </span>,<span class="_ _6"> </span>用于交<span class="_ _1"></span>流信号源<span class="_ _33"> </span>、<span class="_ _d"> </span>电源</div><div class="t m0 x2 h4 y1c ff2 fs1 fc1 sc0 ls0 ws0">变换<span class="_ _c"> </span>、<span class="_ _6"> </span>频率变<span class="_ _1"></span>换<span class="_ _35"> </span>、<span class="_ _6"> </span>脉冲调制等<span class="_ _22"> </span>。<span class="_ _6"> </span>由于它<span class="_ _1"></span>工作可靠<span class="_ _33"> </span>、<span class="_ _6"> </span>使用方<span class="_ _1"></span>便<span class="_ _35"> </span>、<span class="_ _6"> </span>价格低廉<span class="_ _35"> </span>,<span class="_ _6"> </span>目前被广泛<span class="_ _1"></span>用于各</div><div class="t m0 x2 h4 y1d ff2 fs1 fc1 sc0 ls0 ws0">种电子产品<span class="_ _1"></span>中,<span class="_ _33"> </span><span class="ff3">555<span class="_ _2"> </span></span>集成电路内部有<span class="_ _1"></span>几十个元器件<span class="_ _1"></span>,有分压器、<span class="_ _1"></span>比较器、基本<span class="_ _37"> </span><span class="ff3">R-S<span class="_ _38"> </span></span>触发器</div><div class="t m2 x6 h4 y1d ff2 fs1 fc1 sc0 ls0 ws0">、</div><div class="t m0 x2 h4 y1e ff2 fs1 fc1 sc0 ls0 ws0">放电管以及<span class="_ _1"></span>缓冲器等,电<span class="_ _1"></span>路比较复杂,<span class="_ _1"></span>是模拟电路和<span class="_ _1"></span>数字电路的混<span class="_ _1"></span>合体,如图<span class="_ _39"> </span><span class="ff3">1<span class="_ _4"> </span></span>所示。</div><div class="t m0 x2 h4 y1f ff3 fs1 fc1 sc0 ls0 ws0">555<span class="_ _2"> </span><span class="ff2">芯片管脚介<span class="_ _1"></span>绍</span></div><a class="l" rel='nofollow' onclick='return false;'><div class="d m3"></div></a></div><div class="pi" data-data='{"ctm":[1.611830,0.000000,0.000000,1.611830,0.000000,0.000000]}'></div></div>
</body>
</html>
<div id="pf2" class="pf w0 h0" data-page-no="2"><div class="pc pc2 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/624f05916caf596192b82381/bg2.jpg"><div class="t m0 x3 h4 y20 ff3 fs1 fc1 sc0 ls0 ws0">555<span class="_ _2"> </span><span class="ff2">集成电路是<span class="_ _10"> </span></span>8<span class="_ _4"> </span><span class="ff2">脚封装<span class="_ _15"> </span>,<span class="_ _d"> </span>双列直插型<span class="_ _22"> </span>,<span class="_ _d"> </span>如图<span class="_ _12"> </span></span>2(A)<span class="_ _3a"> </span><span class="ff2">所示<span class="_ _c"> </span>,<span class="_ _d"> </span>按输入输出<span class="_ _1"></span>的排列可看成<span class="_ _1"></span>如<span class="_ _3b"> </span>图</span></div><div class="t m0 x2 h4 y21 ff3 fs1 fc1 sc0 ls0 ws0">2(B)<span class="_ _3c"> </span><span class="ff2">所示。其中<span class="_ _10"> </span></span>6<span class="_ _4"> </span><span class="ff2">脚称阈值端<span class="_ _22"> </span></span>(T<span class="_ _3d"></span>H)<span class="_ _c"> </span><span class="ff2">,是上<span class="_ _1"></span>比较器的输入<span class="_ _1"></span>;<span class="_ _20"> </span><span class="ff3">2<span class="_ _4"> </span></span>脚称触发端<span class="_ _22"> </span><span class="ff3">(TR)<span class="_ _3e"> </span></span>,是下比较<span class="_ _1"></span>器的</span></div><div class="t m0 x2 h4 y22 ff2 fs1 fc1 sc0 ls0 ws0">输入<span class="_ _c"> </span>;<span class="_ _23"> </span><span class="ff3">3<span class="_ _3f"> </span></span>脚是输出端</div><div class="t m4 x7 h6 y22 ff3 fs1 fc1 sc0 ls0 ws0">(V<span class="_ _3d"></span>o)</div><div class="t m0 x8 h4 y22 ff2 fs1 fc1 sc0 ls0 ws0">,<span class="_ _23"> </span>它<span class="_ _9"> </span>有<span class="_ _40"> </span><span class="ff3">O<span class="_ _1e"> </span></span>和<span class="_ _41"> </span><span class="ff3">1<span class="_ _3f"> </span></span>两种状态<span class="_ _35"> </span>,<span class="_ _23"> </span>由输入端所加的<span class="_ _1"></span>电平决定<span class="_ _36"> </span>;<span class="_ _23"> </span><span class="ff3">7<span class="_ _3f"> </span></span>脚是放电端<span class="_ _22"> </span><span class="ff3">(DIS)</span></div><div class="t m1 x4 h4 y22 ff2 fs1 fc1 sc0 ls0 ws0">,</div><div class="t m0 x2 h4 y23 ff2 fs1 fc1 sc0 ls0 ws0">它是内部放<span class="_ _1"></span>电管的输出<span class="_ _42"> </span>,<span class="_ _6"> </span>有悬空和接<span class="_ _1"></span>地两种状态<span class="_ _42"> </span>,<span class="_ _6"> </span>也是由<span class="_ _1"></span>输入端的状态<span class="_ _1"></span>决定<span class="_ _36"> </span>;<span class="_ _6"> </span><span class="ff3">4<span class="_ _4"> </span></span>脚是复位端</div><div class="t m0 x2 h4 y4 ff3 fs1 fc1 sc0 ls0 ws0">(MR)<span class="_ _43"> </span><span class="ff2">,<span class="_ _23"> </span>加上低电平时可<span class="_ _1"></span>使输出为低电<span class="_ _1"></span>平<span class="_ _34"> </span>;<span class="_ _44"> </span><span class="ff3">5<span class="_ _4"> </span></span>脚是控制电<span class="_ _1"></span>压端<span class="_ _33"> </span><span class="ff3">(Vc),<span class="_ _45"> </span></span>可用它改变<span class="_ _1"></span>上下触发电平<span class="_ _1"></span>值</span></div><div class="t m1 x4 h4 y4 ff2 fs1 fc1 sc0 ls0 ws0">;</div><div class="t m0 x2 h4 y5 ff3 fs1 fc1 sc0 ls0 ws0">8<span class="_ _4"> </span><span class="ff2">脚是电源端<span class="_ _1"></span>,<span class="_ _26"> </span><span class="ff3">1<span class="_ _2e"> </span></span>脚是地端。</span></div><div class="t m0 x3 h4 y14 ff2 fs1 fc1 sc0 ls0 ws0">图<span class="_ _3"> </span><span class="ff3">2<span class="_ _4"> </span>555<span class="_ _2"> </span></span>集成电路封<span class="_ _1"></span>装图</div><div class="t m0 x3 h4 y15 ff2 fs1 fc1 sc0 ls0 ws0">我们<span class="_ _1"></span>也可以<span class="_ _1"></span>把<span class="_ _46"> </span><span class="ff3">555<span class="_ _2"> </span></span>电路等<span class="_ _1"></span>效成一<span class="_ _1"></span>个带放<span class="_ _1"></span>电开关<span class="_ _1"></span>的<span class="_ _47"> </span><span class="ff3">R-S<span class="_ _38"> </span></span>触发器<span class="_ _1"></span>,如图<span class="_ _46"> </span><span class="ff3">3<span class="_ _1"></span>(A)<span class="_ _3a"> </span><span class="ff2">所示,<span class="_ _1"></span>这个特</span></span></div><div class="t m0 x2 h4 y16 ff2 fs1 fc1 sc0 ls0 ws0">殊的触发器<span class="_ _1"></span>有两个输入端<span class="_ _36"> </span>:<span class="_ _d"> </span>阈值端<span class="_ _15"> </span><span class="ff3">(TH)<span class="_ _c"> </span></span>可看成<span class="_ _1"></span>是置零端<span class="_ _13"> </span><span class="ff3">R<span class="_ _48"> </span></span>,<span class="_ _d"> </span>要求高电平<span class="_ _22"> </span>,<span class="_ _d"> </span>触发端<span class="_ _15"> </span><span class="ff3">(TR)<span class="_ _3e"> </span></span>可<span class="_ _1"></span>看成</div><div class="t m0 x2 h4 y17 ff2 fs1 fc1 sc0 ls0 ws0">是置位端<span class="_ _e"> </span><span class="ff3">S<span class="_ _49"> </span></span>,<span class="_ _d"> </span>要求低电平<span class="_ _22"> </span>,<span class="_ _d"> </span>有一个输出<span class="_ _1"></span>端</div><div class="t m5 x9 h6 y17 ff3 fs1 fc1 sc0 ls0 ws0">V<span class="_ _3d"></span>o</div><div class="t m0 xa h4 y17 ff2 fs1 fc1 sc0 ls0 ws0">,<span class="_ _d"> </span><span class="ff3">V<span class="_ _4a"></span>o<span class="_ _4b"> </span></span>可等效成触<span class="_ _1"></span>发器的<span class="_ _4c"> </span><span class="ff3">Q<span class="_ _27"> </span></span>端<span class="_ _9"> </span>,<span class="_ _d"> </span>放电端<span class="_ _15"> </span><span class="ff3">(DIS)<span class="_ _4d"> </span></span>可看</div><div class="t m0 x2 h4 y18 ff2 fs1 fc1 sc0 ls0 ws0">成是由内部<span class="_ _1"></span>放电开关控制<span class="_ _1"></span>的一个接点,<span class="_ _1"></span>由触发器的<span class="_ _4e"> </span><span class="ff3">Q<span class="_ _27"> </span></span>端控制<span class="_ _1"></span>:<span class="_ _19"> </span><span class="ff3">Q=1<span class="_ _3a"> </span></span>时<span class="_ _3"> </span><span class="ff3">DI<span class="_ _3d"></span>S<span class="_ _4f"> </span></span>端接地,<span class="_ _35"> </span><span class="ff3">Q=0<span class="_ _50"> </span></span>时</div><div class="t m0 x2 h4 y19 ff3 fs1 fc1 sc0 ls0 ws0">DIS<span class="_ _a"> </span><span class="ff2">端悬空。另外还<span class="_ _1"></span>有复位端<span class="_ _51"> </span><span class="ff3">MR<span class="_ _52"> </span></span>,控制电压<span class="_ _1"></span>端<span class="_ _1b"> </span><span class="ff3">Vc<span class="_ _53"> </span></span>,电源端<span class="_ _e"> </span><span class="ff3">VDD<span class="_ _4d"> </span></span>和</span></div><div class="t m0 x2 h4 y1a ff2 fs1 fc1 sc0 ls0 ws0">地端<span class="_ _12"> </span><span class="ff3">GND<span class="_ _b"> </span></span>。这个<span class="_ _1"></span>特殊的触发器<span class="_ _1"></span>有两个特点:</div><div class="t m0 x2 h4 y1b ff3 fs1 fc1 sc0 ls0 ws0">(1)<span class="_ _53"> </span><span class="ff2">两个<span class="_ _1"></span>输入<span class="_ _1"></span>端<span class="_ _1"></span>的触<span class="_ _1"></span>发<span class="_ _1"></span>电平<span class="_ _1"></span>要<span class="_ _1"></span>求一<span class="_ _1"></span>高<span class="_ _1"></span>一低<span class="_ _1"></span>,<span class="_ _1"></span>置零<span class="_ _1"></span>端<span class="_ _54"> </span><span class="ff3">R<span class="_ _1e"> </span></span>即阈值<span class="_ _1"></span>端<span class="_ _55"> </span><span class="ff3">(TH)<span class="_ _c"> </span></span>要求<span class="_ _1"></span>高电<span class="_ _1"></span>平<span class="_ _1"></span>,而<span class="_ _1"></span>置<span class="_ _1"></span>位端<span class="_ _56"> </span><span class="ff3">s</span></span></div><div class="t m0 x2 h4 y1c ff2 fs1 fc1 sc0 ls0 ws0">即触发端<span class="_ _35"> </span><span class="ff3">(TR)<span class="_ _57"> </span></span>则要求低电<span class="_ _1"></span>乎<span class="_ _26"> </span><span class="ff3">;</span></div><div class="t m0 x2 h4 y1d ff3 fs1 fc1 sc0 ls0 ws0">(2)<span class="_ _53"> </span><span class="ff2">两个输入端<span class="_ _1"></span>的触发电平使<span class="_ _1"></span>输出发生翻转<span class="_ _1"></span>的阈值电压值<span class="_ _1"></span>也不同<span class="_ _58"> </span>,<span class="_ _9"> </span>当<span class="_ _3"> </span><span class="ff3">V<span class="_ _59"> </span>c<span class="_ _3f"> </span></span>端不接<span class="_ _1"></span>控制电压时</span></div><div class="t m1 x4 h4 y1d ff2 fs1 fc1 sc0 ls0 ws0">,</div><div class="t m0 x2 h4 y1e ff2 fs1 fc1 sc0 ls0 ws0">对<span class="_ _3"> </span><span class="ff3">TH(R)<span class="_ _5a"> </span></span>端来讲<span class="_ _15"> </span>,<span class="_ _d"> </span><span class="ff3">>2/3VD<span class="_ _1"></span>D<span class="_ _5b"> </span><span class="ff2">是高电平<span class="_ _e"> </span></span>1,<2/3VDD<span class="_ _5c"> </span><span class="ff2">是低电平<span class="_ _e"> </span></span>0<span class="_ _8"> </span><span class="ff2">:<span class="_ _d"> </span>而<span class="_ _1"></span>对<span class="_ _12"> </span><span class="ff3">T<span class="_ _3d"></span>R(S)<span class="_ _5d"> </span></span>端来讲<span class="_ _15"> </span>,<span class="_ _d"> </span><span class="ff3">>1/3VD<span class="_ _5e"> </span>D</span></span></span></div><div class="t m0 x2 h4 y24 ff2 fs1 fc1 sc0 ls0 ws0">是高电<span class="_ _1"></span>平<span class="_ _5f"> </span><span class="ff3">1<span class="_ _8"> </span></span>,<span class="_ _9"> </span><span class="ff3"><1/3VDD<span class="_ _5b"> </span></span>是低电平<span class="_ _5b"> </span><span class="ff3">0<span class="_ _8"> </span></span>。如果<span class="_ _1"></span>在控制<span class="_ _1"></span>端<span class="_ _2b"> </span><span class="ff3">(Vc)<span class="_ _3c"> </span></span>上控制电<span class="_ _1"></span>压<span class="_ _60"> </span><span class="ff3">Vc<span class="_ _11"> </span></span>时,这<span class="_ _1"></span>时上触发<span class="_ _1"></span>电平</div><div class="t m0 x2 h4 y25 ff2 fs1 fc1 sc0 ls0 ws0">就变成<span class="_ _7"> </span><span class="ff3">Vc<span class="_ _11"> </span></span>值<span class="_ _9"> </span>,<span class="_ _9"> </span>下<span class="_ _1"></span>触发电平就变成<span class="_ _4c"> </span><span class="ff3">1/2Vc<span class="_ _61"> </span></span>值<span class="_ _9"> </span>,<span class="_ _9"> </span>可<span class="_ _62"> </span>见改变控制<span class="_ _1"></span>端的控制电压<span class="_ _1"></span>值就可以改变<span class="_ _1"></span>上</div><div class="t m0 x2 h4 y26 ff2 fs1 fc1 sc0 ls0 ws0">下触发电平<span class="_ _1"></span>值。它的功能<span class="_ _1"></span>表见图<span class="_ _63"> </span><span class="ff3">3(B)<span class="_ _3c"> </span></span>所示。</div><a class="l" rel='nofollow' onclick='return false;'><div class="d m3"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m3"></div></a></div><div class="pi" data-data='{"ctm":[1.611830,0.000000,0.000000,1.611830,0.000000,0.000000]}'></div></div>
<div id="pf3" class="pf w0 h0" data-page-no="3"><div class="pc pc3 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/624f05916caf596192b82381/bg3.jpg"><div class="t m0 x2 h4 y21 ff2 fs1 fc1 sc0 ls0 ws0">图<span class="_ _3"> </span><span class="ff3">3<span class="_ _4"> </span>555<span class="_ _2"> </span></span>电路等效<span class="_ _e"> </span><span class="ff3">R<span class="_ _64"> </span></span>—<span class="_ _9"> </span><span class="ff3">S<span class="_ _48"> </span></span>触发器</div><div class="t m0 x3 h4 y22 ff3 fs1 fc1 sc0 ls0 ws0">555<span class="_ _2"> </span><span class="ff2">集成电<span class="_ _1"></span>路有双<span class="_ _1"></span>极型和<span class="_ _65"> </span><span class="ff3">CMOS<span class="_ _17"> </span></span>型两种<span class="_ _1"></span>。<span class="_ _66"> </span><span class="ff3">CMOS<span class="_ _17"> </span></span>型的优<span class="_ _1"></span>点是功<span class="_ _1"></span>耗低、<span class="_ _1"></span>电源电<span class="_ _1"></span>压低、<span class="_ _1"></span>输</span></div><div class="t m0 x2 h4 y23 ff2 fs1 fc1 sc0 ls0 ws0">入阻抗高<span class="_ _35"> </span>,<span class="_ _d"> </span>但输出功率<span class="_ _1"></span>较小<span class="_ _33"> </span>,<span class="_ _d"> </span>输出驱动电<span class="_ _1"></span>流只有几毫安<span class="_ _36"> </span>。<span class="_ _d"> </span>双<span class="_ _1"></span>极型的优点是<span class="_ _1"></span>输出功率大<span class="_ _3b"> </span>,<span class="_ _67"> </span>驱动</div><div class="t m0 x2 h4 y4 ff2 fs1 fc1 sc0 ls0 ws0">电流达<span class="_ _7"> </span><span class="ff3">200<span class="_ _2"> </span></span>毫安,其他指标<span class="_ _1"></span>则不如<span class="_ _1d"> </span><span class="ff3">CMOS<span class="_ _17"> </span></span>型的。</div><div class="t m0 x2 h4 y5 ff3 fs1 fc1 sc0 ls0 ws0">4.<span class="_ _9"> </span><span class="ff2">典型应用电<span class="_ _1"></span>路</span></div><div class="t m0 x3 h4 y7 ff3 fs1 fc1 sc0 ls0 ws0">555<span class="_ _2"> </span><span class="ff2">的应用电路<span class="_ _1"></span>很多<span class="_ _33"> </span>,<span class="_ _d"> </span>只要改变<span class="_ _e"> </span><span class="ff3">555<span class="_ _2"> </span></span>集成电路的外部<span class="_ _1"></span>附加电路<span class="_ _36"> </span>,<span class="_ _d"> </span>就可以构成<span class="_ _1"></span>几百种应用</span></div><div class="t m0 x2 h4 y8 ff2 fs1 fc1 sc0 ls0 ws0">电路,大体<span class="_ _1"></span>上可分为<span class="_ _31"> </span><span class="ff3">555<span class="_ _2"> </span></span>单稳、<span class="_ _15"> </span><span class="ff3">555<span class="_ _2"> </span></span>双稳及<span class="_ _7"> </span><span class="ff3">555<span class="_ _2"> </span></span>无稳<span class="_ _c"> </span><span class="ff3">(<span class="_ _68"> </span></span>即振荡器<span class="_ _35"> </span><span class="ff3">)<span class="_ _68"> </span></span>三类。</div><div class="t m0 x2 h4 yc ff3 fs1 fc1 sc0 ls0 ws0">5<span class="_ _9"> </span>555<span class="_ _2"> </span><span class="ff2">单稳电路</span></div><div class="t m0 x3 h4 yd ff2 fs1 fc1 sc0 ls0 ws0">单稳电路有<span class="_ _1"></span>一个稳态和一<span class="_ _1"></span>个暂稳态<span class="_ _69"> </span>,<span class="_ _6a"> </span>是利用电容<span class="_ _1"></span>的充放电形成<span class="_ _1"></span>暂稳态的<span class="_ _69"> </span>,<span class="_ _6a"> </span>因此它的输入</div><div class="t m0 x2 h4 ye ff2 fs1 fc1 sc0 ls0 ws0">端都带有定<span class="_ _1"></span>时电阻和定时<span class="_ _1"></span>电容,常见的<span class="_ _6b"> </span><span class="ff3">555<span class="_ _2"> </span></span>单稳电路有两种<span class="_ _1"></span>:</div><div class="t m0 xb h4 yf ff3 fs1 fc1 sc0 ls0 ws0">1)<span class="_ _59"> </span><span class="ff2">人工启<span class="_ _1"></span>动型</span></div><div class="t m0 xb h4 y10 ff2 fs1 fc1 sc0 ls0 ws0">将<span class="_ _3"> </span><span class="ff3">555<span class="_ _6c"> </span></span>电路<span class="_ _1"></span>的<span class="_ _6d"> </span><span class="ff3">6<span class="_ _8"> </span></span>、<span class="_ _6e"> </span><span class="ff3">2<span class="_ _4"> </span></span>脚并接<span class="_ _1"></span>起<span class="_ _1"></span>来接<span class="_ _1"></span>在<span class="_ _6f"> </span><span class="ff3">RC<span class="_ _70"> </span></span>定时<span class="_ _1"></span>电<span class="_ _1"></span>路上<span class="_ _1"></span>,<span class="_ _1"></span>在定<span class="_ _1"></span>时<span class="_ _1"></span>电容<span class="_ _71"> </span><span class="ff3">CT<span class="_ _11"> </span></span>,<span class="_ _1"></span>两端<span class="_ _1"></span>接<span class="_ _1"></span>按钮<span class="_ _1"></span>开<span class="_ _13"> </span>关</div><div class="t m0 x2 h4 y11 ff3 fs1 fc1 sc0 ls0 ws0">SB<span class="_ _4b"> </span><span class="ff2">,<span class="_ _d"> </span>就成为人工启动<span class="_ _1"></span>型<span class="_ _72"> </span><span class="ff3">555<span class="_ _2"> </span></span>单稳电路<span class="_ _35"> </span>,<span class="_ _6"> </span>如图<span class="_ _12"> </span><span class="ff3">4(a)<span class="_ _30"> </span></span>所示<span class="_ _c"> </span>,<span class="_ _6"> </span>用等效触发<span class="_ _1"></span>器替代<span class="_ _4c"> </span><span class="ff3">555<span class="_ _62"> </span></span>,<span class="_ _6"> </span>并略去与单</span></div><div class="t m0 x2 h4 y12 ff2 fs1 fc1 sc0 ls0 ws0">稳工作无关<span class="_ _1"></span>的部分后见图<span class="_ _2f"> </span><span class="ff3">4(b)<span class="_ _73"> </span></span>所示,下面<span class="_ _1"></span>分析它的工作<span class="_ _1"></span>原理:</div><div class="t m0 x3 h4 y13 ff2 fs1 fc1 sc0 ls0 ws0">稳态<span class="_ _c"> </span>:<span class="_ _67"> </span>接上电源后<span class="_ _22"> </span>,<span class="_ _67"> </span>电容<span class="_ _74"> </span><span class="ff3">CT<span class="_ _75"> </span></span>很快充电到<span class="_ _10"> </span><span class="ff3">VDD<span class="_ _b"> </span></span>,<span class="_ _67"> </span>从图<span class="_ _12"> </span><span class="ff3">4(b)<span class="_ _73"> </span></span>看到<span class="_ _c"> </span>,<span class="_ _d"> </span>触发器输入<span class="_ _10"> </span><span class="ff3">R=1<span class="_ _a"> </span></span>,<span class="_ _d"> </span><span class="ff3">S=1</span></div><div class="t m1 x4 h4 y13 ff2 fs1 fc1 sc0 ls0 ws0">,</div><div class="t m0 x2 h4 y14 ff2 fs1 fc1 sc0 ls0 ws0">从功能表看<span class="_ _1"></span>到输出<span class="_ _4c"> </span><span class="ff3">V<span class="_ _4a"></span>o=0<span class="_ _b"> </span></span>,<span class="_ _1"></span>这是它的稳态<span class="_ _1"></span>。</div><div class="t m0 x3 h4 y15 ff2 fs1 fc1 sc0 ls0 ws0">暂稳态<span class="_ _15"> </span>:<span class="_ _9"> </span>按下开<span class="_ _1"></span>关<span class="_ _e"> </span><span class="ff3">S<span class="_ _3d"></span>B<span class="_ _4b"> </span></span>,<span class="_ _76"> </span><span class="ff3">CT<span class="_ _75"> </span></span>上电荷很快<span class="_ _1"></span>放到零<span class="_ _1f"> </span>,<span class="_ _9"> </span>相当于触发器输<span class="_ _1"></span>入<span class="_ _4c"> </span><span class="ff3">R=<span class="_ _3d"></span>0<span class="_ _a"> </span></span>,<span class="_ _9"> </span><span class="ff3">S=0<span class="_ _2"> </span></span>,<span class="_ _9"> </span>输出立</div><div class="t m0 x2 h4 y16 ff2 fs1 fc1 sc0 ls0 ws0">即翻转<span class="_ _1"></span>成</div><div class="t m6 xc h6 y16 ff3 fs1 fc1 sc0 ls0 ws0">V<span class="_ _77"></span>o<span class="_ _1"></span>=<span class="_ _1"></span>l</div><div class="t m0 xd h4 y16 ff2 fs1 fc1 sc0 ls0 ws0">,暂稳<span class="_ _1"></span>态开始<span class="_ _1"></span>。开关<span class="_ _1"></span>放开后<span class="_ _1"></span>,电源<span class="_ _1"></span>又向<span class="_ _78"> </span><span class="ff3">CT<span class="_ _75"> </span></span>充电,经<span class="_ _1"></span>过时间<span class="_ _79"> </span><span class="ff3">TD<span class="_ _70"> </span></span>后<span class="_ _1"></span>,<span class="_ _7a"> </span><span class="ff3">CT<span class="_ _75"> </span></span>上电</div><div class="t m0 x2 h4 y17 ff2 fs1 fc1 sc0 ls0 ws0">压上升到<span class="_ _35"> </span><span class="ff3">>2/3VDD<span class="_ _e"> </span></span>时,输出又翻转<span class="_ _1"></span>成<span class="_ _72"> </span><span class="ff3">V<span class="_ _4a"> </span>o=O<span class="_ _7b"> </span></span>,暂稳态结<span class="_ _1"></span>束。<span class="_ _7c"> </span><span class="ff3">TD<span class="_ _7d"> </span></span>就是单稳电<span class="_ _1"></span>路的定时时间<span class="_ _1"></span>或</div><div class="t m0 x2 h4 y18 ff2 fs1 fc1 sc0 ls0 ws0">延时时间,<span class="_ _1"></span>它和定时电阻<span class="_ _2f"> </span><span class="ff3">R<span class="_ _3d"></span>T<span class="_ _f"> </span></span>和定时电容<span class="_ _10"> </span><span class="ff3">CT<span class="_ _75"> </span></span>的值有关:<span class="_ _22"> </span><span class="ff3">TD=1.1R<span class="_ _3d"></span>TCT<span class="_ _7e"> </span></span>。</div><div class="t m0 x3 h4 y27 ff2 fs1 fc1 sc0 ls0 ws0">图<span class="_ _3"> </span><span class="ff3">4<span class="_ _4"> </span></span>人工启动型<span class="_ _10"> </span><span class="ff3">555<span class="_ _30"> </span></span>单稳电路</div><div class="t m0 x3 h4 y28 ff3 fs1 fc1 sc0 ls0 ws0">2)<span class="_ _59"> </span><span class="ff2">脉<span class="_ _1"></span>冲启动型</span></div><div class="t m0 x3 h4 y29 ff2 fs1 fc1 sc0 ls0 ws0">将<span class="_ _3"> </span><span class="ff3">555<span class="_ _2"> </span></span>电路的<span class="_ _7f"> </span><span class="ff3">6<span class="_ _8"> </span></span>、<span class="_ _9"> </span><span class="ff3">7<span class="_ _2e"> </span></span>脚并接起<span class="_ _1"></span>来接在<span class="_ _1"></span>定时电<span class="_ _1"></span>容<span class="_ _80"> </span><span class="ff3">CT<span class="_ _75"> </span></span>上,用<span class="_ _7f"> </span><span class="ff3">2<span class="_ _4"> </span></span>脚作输入<span class="_ _1"></span>就成为<span class="_ _1"></span>脉冲启<span class="_ _1"></span>动型</div><div class="t m0 x2 h4 y2a ff2 fs1 fc1 sc0 ls0 ws0">单稳电路<span class="_ _35"> </span>,<span class="_ _d"> </span>如图<span class="_ _12"> </span><span class="ff3">5(a)<span class="_ _30"> </span></span>所示<span class="_ _c"> </span>,<span class="_ _d"> </span>电路的<span class="_ _7f"> </span><span class="ff3">2<span class="_ _4"> </span></span>脚平时接高<span class="_ _1"></span>电平<span class="_ _33"> </span>,<span class="_ _d"> </span>当输入接低电平或输<span class="_ _1"></span>入负脉冲时才<span class="_ _1"></span>启</div><div class="t m0 x2 h4 y2b ff2 fs1 fc1 sc0 ls0 ws0">动电路,用<span class="_ _1"></span>等效触发器替<span class="_ _1"></span>代<span class="_ _16"> </span><span class="ff3">555<span class="_ _2"> </span></span>后见图<span class="_ _7"> </span><span class="ff3">5<span class="_ _4"> </span>6)<span class="_ _59"> </span></span>所示,下面<span class="_ _1"></span>分析它的工作<span class="_ _1"></span>原理:</div><div class="t m0 x3 h4 y2c ff2 fs1 fc1 sc0 ls0 ws0">稳态<span class="_ _1"></span>:<span class="_ _1"></span>接上<span class="_ _1"></span>电<span class="_ _1"></span>源后<span class="_ _1"></span>,<span class="_ _31"> </span><span class="ff3">R<span class="_ _3d"></span>=1<span class="_ _4f"> </span></span>,<span class="_ _9"> </span><span class="ff3">S=1<span class="_ _6c"> </span></span>,输<span class="_ _1"></span>出<span class="_ _29"> </span><span class="ff3">V<span class="_ _4a"> </span>o=0<span class="_ _b"> </span></span>,<span class="_ _6e"> </span><span class="ff3">DIS<span class="_ _4f"> </span></span>端接<span class="_ _1"></span>地<span class="_ _1"></span>,<span class="_ _55"> </span><span class="ff3">CT<span class="_ _75"> </span></span>上的<span class="_ _1"></span>电压<span class="_ _1"></span>为<span class="_ _0"> </span><span class="ff3">0<span class="_ _4"> </span></span>即<span class="_ _81"> </span><span class="ff3">R=0<span class="_ _a"> </span></span>,</div><div class="t m0 x2 h4 y2d ff2 fs1 fc1 sc0 ls0 ws0">输出仍保持<span class="_ _10"> </span><span class="ff3">V<span class="_ _77"></span>o<span class="_ _3d"></span>=0<span class="_ _b"> </span></span>,这是<span class="_ _1"></span>它的稳态。</div><div class="t m0 x3 h4 y2e ff2 fs1 fc1 sc0 ls0 ws0">暂稳态<span class="_ _15"> </span>:<span class="_ _76"> </span>输入负脉冲后<span class="_ _26"> </span>,<span class="_ _9"> </span>输入<span class="_ _74"> </span><span class="ff3">S=0<span class="_ _30"> </span></span>,<span class="_ _9"> </span>输出立即翻转成<span class="_ _13"> </span><span class="ff3">V<span class="_ _4a"> </span>o=1<span class="_ _b"> </span></span>,<span class="_ _76"> </span><span class="ff3">DIS<span class="_ _4f"> </span></span>端开路<span class="_ _15"> </span>,<span class="_ _9"> </span>电源通过</div><div class="t m6 xe h6 y2e ff3 fs1 fc1 sc0 ls0 ws0">R</div><div class="t m0 xf h6 y2e ff3 fs1 fc1 sc0 ls0 ws0">T</div><div class="t m0 x2 h4 y1f ff2 fs1 fc1 sc0 ls0 ws0">向<span class="_ _3"> </span><span class="ff3">CT<span class="_ _75"> </span></span>充电<span class="_ _c"> </span>,<span class="_ _59"> </span>暂稳态<span class="_ _1"></span>开始<span class="_ _82"> </span>。<span class="_ _59"> </span>经过时<span class="_ _1"></span>间<span class="_ _5b"> </span><span class="ff3">TD<span class="_ _7d"> </span></span>后<span class="_ _76"> </span>,<span class="_ _59"> </span><span class="ff3">CT<span class="_ _75"> </span></span>上电压上升<span class="_ _1"></span>到<span class="_ _83"> </span><span class="ff3">>2/3VDD<span class="_ _e"> </span></span>时<span class="_ _9"> </span>,<span class="_ _59"> </span>输入又成为<span class="_ _10"> </span><span class="ff3">R=1</span></div><div class="t m1 x4 h4 y1f ff2 fs1 fc1 sc0 ls0 ws0">,</div><a class="l" rel='nofollow' onclick='return false;'><div class="d m3"></div></a></div><div class="pi" data-data='{"ctm":[1.611830,0.000000,0.000000,1.611830,0.000000,0.000000]}'></div></div>
<div id="pf4" class="pf w0 h0" data-page-no="4"><div class="pc pc4 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/624f05916caf596192b82381/bg4.jpg"><div class="t m0 x2 h4 y20 ff3 fs1 fc1 sc0 ls0 ws0">S=1<span class="_ _2"> </span><span class="ff2">,这<span class="_ _1"></span>时<span class="_ _1"></span>负脉<span class="_ _1"></span>冲<span class="_ _1"></span>已经<span class="_ _1"></span>消<span class="_ _1"></span>失,<span class="_ _1"></span>输<span class="_ _1"></span>出又<span class="_ _1"></span>翻<span class="_ _1"></span>转成<span class="_ _84"> </span><span class="ff3">V<span class="_ _4a"></span>o=0<span class="_ _b"> </span></span>,暂<span class="_ _1"></span>稳态<span class="_ _1"></span>结<span class="_ _1"></span>束。<span class="_ _1"></span>这<span class="_ _1"></span>时内<span class="_ _1"></span>部<span class="_ _1"></span>放电<span class="_ _1"></span>开<span class="_ _1"></span>关接<span class="_ _1"></span>通</span></div><div class="t m7 x6 h4 y20 ff2 fs1 fc1 sc0 ls0 ws0">,</div><div class="t m0 x2 h4 y21 ff3 fs1 fc1 sc0 ls0 ws0">DIS<span class="_ _85"> </span><span class="ff2">端<span class="_ _86"></span>接<span class="_ _86"></span>地<span class="_ _86"></span>,<span class="_ _87"> </span><span class="ff3">CT<span class="_ _7d"> </span></span>上<span class="_ _86"></span>电<span class="_ _88"></span>荷<span class="_ _86"></span>很<span class="_ _86"></span>快<span class="_ _88"></span>放<span class="_ _86"></span>到<span class="_ _88"></span>零<span class="_ _86"></span>,<span class="_ _88"></span>为<span class="_ _86"></span>下<span class="_ _88"></span>一<span class="_ _86"></span>次<span class="_ _88"></span>定<span class="_ _86"></span>时<span class="_ _86"></span>控<span class="_ _88"></span>制<span class="_ _86"></span>作<span class="_ _88"></span>准<span class="_ _86"></span>备<span class="_ _88"></span>。<span class="_ _86"></span>电<span class="_ _88"></span>路<span class="_ _86"></span>的<span class="_ _86"></span>定<span class="_ _88"></span>时<span class="_ _86"></span>时<span class="_ _89"> </span>间</span></div><div class="t m0 x2 h4 y22 ff3 fs1 fc1 sc0 ls0 ws0">TD=1.1RT<span class="_ _3d"></span>CT<span class="_ _7e"> </span><span class="ff2">。</span></div><div class="t m0 x3 h4 y23 ff2 fs1 fc1 sc0 ls0 ws0">这两种单稳<span class="_ _1"></span>电路常用作定<span class="_ _1"></span>时延时控制。</div><div class="t m0 x3 h4 y12 ff2 fs1 fc1 sc0 ls0 ws0">图<span class="_ _3"> </span><span class="ff3">5<span class="_ _4"> </span></span>脉冲启动型<span class="_ _1"></span>单稳电路</div><div class="t m0 x2 h4 y14 ff3 fs1 fc1 sc0 ls0 ws0">6<span class="_ _9"> </span>555<span class="_ _2"> </span><span class="ff2">双稳电路</span></div><div class="t m0 x3 h4 y15 ff2 fs1 fc1 sc0 ls0 ws0">常见的<span class="_ _7"> </span><span class="ff3">555<span class="_ _2"> </span></span>双稳电路有两种<span class="_ _1"></span>:</div><div class="t m0 x3 h4 y16 ff3 fs1 fc1 sc0 ls0 ws0">1)R-S<span class="_ _8a"> </span><span class="ff2">触发器型双<span class="_ _1"></span>稳</span></div><div class="t m0 x3 h4 y17 ff2 fs1 fc1 sc0 ls0 ws0">将<span class="_ _3"> </span><span class="ff3">555<span class="_ _2"> </span></span>电路的<span class="_ _7f"> </span><span class="ff3">6<span class="_ _8"> </span></span>、<span class="_ _9"> </span><span class="ff3">2<span class="_ _2e"> </span></span>脚作为<span class="_ _1"></span>两个控<span class="_ _1"></span>制输入<span class="_ _1"></span>端,<span class="_ _8b"> </span><span class="ff3">7<span class="_ _4"> </span></span>端不用,<span class="_ _1"></span>就成为<span class="_ _1"></span>一个<span class="_ _8c"> </span><span class="ff3">R-S<span class="_ _38"> </span></span>触发器。<span class="_ _1"></span>注意</div><div class="t m0 x2 h4 y18 ff2 fs1 fc1 sc0 ls0 ws0">两个输入端<span class="_ _1"></span>的触发电平和<span class="_ _1"></span>阈值电压不同<span class="_ _8d"> </span>,<span class="_ _d"> </span>如图<span class="_ _12"> </span><span class="ff3">6(a)<span class="_ _30"> </span></span>所示<span class="_ _c"> </span>,<span class="_ _d"> </span>有时可能只有一个控<span class="_ _1"></span>制端<span class="_ _36"> </span>,<span class="_ _d"> </span>这时另</div><div class="t m0 x2 h4 y19 ff2 fs1 fc1 sc0 ls0 ws0">外一<span class="_ _1"></span>个控制<span class="_ _1"></span>端要设<span class="_ _1"></span>法接死<span class="_ _1"></span>,根据<span class="_ _1"></span>电路要<span class="_ _1"></span>求可以<span class="_ _1"></span>把<span class="_ _8e"> </span><span class="ff3">R<span class="_ _1e"> </span></span>端接到电<span class="_ _1"></span>源端,<span class="_ _1"></span>如图<span class="_ _65"> </span><span class="ff3">6(b)<span class="_ _73"> </span></span>所示,<span class="_ _1"></span>也可以</div><div class="t m0 x2 h4 y1a ff2 fs1 fc1 sc0 ls0 ws0">把<span class="_ _3"> </span><span class="ff3">S<span class="_ _48"> </span></span>接地,用<span class="_ _e"> </span><span class="ff3">R<span class="_ _1e"> </span></span>端作输<span class="_ _1"></span>入。</div><div class="t m0 x3 h4 y1b ff2 fs1 fc1 sc0 ls0 ws0">有两个输入<span class="_ _1"></span>端的双稳电路<span class="_ _1"></span>常用作电机调<span class="_ _1"></span>速<span class="_ _8f"> </span>、<span class="_ _6a"> </span>电源上下限告警<span class="_ _1"></span>等用途<span class="_ _42"> </span>。<span class="_ _6a"> </span>有一个输入端的双</div><div class="t m0 x2 h4 y1c ff2 fs1 fc1 sc0 ls0 ws0">稳电路作为<span class="_ _1"></span>单端比较器用<span class="_ _1"></span>于各种检测电<span class="_ _1"></span>路。</div><div class="t m0 x3 h4 y2a ff2 fs1 fc1 sc0 ls0 ws0">图<span class="_ _3"> </span><span class="ff3">6<span class="_ _4"> </span>555<span class="_ _2"> </span></span>构成<span class="_ _12"> </span><span class="ff3">R-S<span class="_ _38"> </span></span>触发器</div><div class="t m0 x3 h4 y2b ff3 fs1 fc1 sc0 ls0 ws0">2)<span class="_ _59"> </span><span class="ff2">施<span class="_ _1"></span>密特触发器型<span class="_ _1"></span>双稳</span></div><div class="t m0 x3 h4 y2c ff2 fs1 fc1 sc0 ls0 ws0">将<span class="_ _3"> </span><span class="ff3">555<span class="_ _2"> </span></span>电路的<span class="_ _7"> </span><span class="ff3">6<span class="_ _90"> </span></span>、<span class="_ _9"> </span><span class="ff3">2<span class="_ _4"> </span></span>脚并接起来<span class="_ _1"></span>接成只<span class="_ _1"></span>有一个<span class="_ _1"></span>输入端<span class="_ _1"></span>的触发<span class="_ _1"></span>器,如<span class="_ _1"></span>图<span class="_ _91"> </span><span class="ff3">7(a)<span class="_ _30"> </span></span>所示,这<span class="_ _1"></span>个触</div><div class="t m0 x2 h4 y2d ff2 fs1 fc1 sc0 ls0 ws0">发器输出电<span class="_ _1"></span>压和输入电压<span class="_ _1"></span>的关系是一个<span class="_ _1"></span>长方形的回线<span class="_ _1"></span>形<span class="_ _92"> </span>,<span class="_ _67"> </span>如图<span class="_ _74"> </span><span class="ff3">7(b)<span class="_ _73"> </span></span>所示<span class="_ _c"> </span>,<span class="_ _67"> </span>从曲线可知<span class="_ _22"> </span>,<span class="_ _d"> </span>当输</div><div class="t m0 x2 h4 y2e ff2 fs1 fc1 sc0 ls0 ws0">入<span class="_ _3"> </span><span class="ff3">V1=0<span class="_ _2a"> </span></span>时输出<span class="_ _7"> </span><span class="ff3">V<span class="_ _4a"> </span>o=1<span class="_ _b"> </span></span>,当输入电<span class="_ _1"></span>压从<span class="_ _93"> </span><span class="ff3">0<span class="_ _4"> </span></span>上升到<span class="_ _15"> </span><span class="ff3">>2/3VDD<span class="_ _e"> </span></span>后,<span class="_ _c"> </span><span class="ff3">V<span class="_ _4a"> </span>o<span class="_ _4b"> </span></span>翻转成<span class="_ _7"> </span><span class="ff3">0<span class="_ _8"> </span></span>,当输入电压从<span class="_ _1"></span>最</div><div class="t m0 x2 h4 y1f ff2 fs1 fc1 sc0 ls0 ws0">高值下<span class="_ _1"></span>降到<span class="_ _94"> </span><span class="ff3"><1/3VDD<span class="_ _e"> </span></span>后,<span class="_ _c"> </span><span class="ff3">V<span class="_ _4a"> </span>o<span class="_ _4b"> </span></span>又翻转成<span class="_ _5b"> </span><span class="ff3">1<span class="_ _8"> </span></span>。由于它<span class="_ _1"></span>的输入<span class="_ _1"></span>有两个<span class="_ _1"></span>不同的<span class="_ _1"></span>阈值电<span class="_ _1"></span>压,所<span class="_ _1"></span>以,这</div><a class="l" rel='nofollow' onclick='return false;'><div class="d m3"></div></a><a class="l" rel='nofollow' onclick='return false;'><div class="d m3"></div></a></div><div class="pi" data-data='{"ctm":[1.611830,0.000000,0.000000,1.611830,0.000000,0.000000]}'></div></div>