电子基础2.htm

电 流： 电荷的定向移动叫做电流。电路中

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            lang=EN-US style="COLOR: black; FONT-FAMILY: 宋体">ISV59.OSV70/IS2208 
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            style="COLOR: black; FONT-FAMILY: 宋体">日本<SPAN lang=EN-US> 
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            lang=EN-US style="COLOR: black; FONT-FAMILY: 宋体">3 </SPAN></P></TD>
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            <P class=MsoNormal style="TEXT-ALIGN: center" align=center><SPAN 
            lang=EN-US style="COLOR: black; FONT-FAMILY: 宋体">5.5 </SPAN></P></TD>
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            <P class=MsoNormal style="TEXT-ALIGN: center" align=center><SPAN 
            lang=EN-US style="COLOR: black; FONT-FAMILY: 宋体">UHF 
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      <DIV align=center><BR><SPAN lang=EN-US><A 
      href="http://league.ysu.edu.cn/wuxie/dzjc/ejg.asp#top"><SPAN 
      style="FONT-FAMILY: 宋体">返回顶部</SPAN></A></SPAN> </DIV>
      <P class=MsoNormal style="TEXT-ALIGN: left" align=center><A 
      name=3><STRONG>3.二极管的选用常识</STRONG></A></P>
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            <P class=MsoNormal style="LINE-HEIGHT: 15pt"><SPAN 
            style="COLOR: black; FONT-FAMILY: 宋体; Times: ">选用三极管要注意的几个方面：</SPAN><SPAN 
            lang=EN-US style="COLOR: black"> </SPAN><BR><SPAN 
            style="COLOR: blue; FONT-FAMILY: 宋体; Times: ">（</SPAN><SPAN 
            lang=EN-US style="COLOR: blue">1</SPAN><SPAN 
            style="COLOR: blue; FONT-FAMILY: 宋体; Times: ">）正向特性</SPAN><SPAN 
            lang=EN-US style="COLOR: black; FONT-FAMILY: 宋体"> </SPAN></P></TD></TR>
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            <P class=MsoNormal style="LINE-HEIGHT: 15pt"><SPAN 
            style="FONT-FAMILY: 宋体">另在二极管两端的正向电压（</SPAN><SPAN 
            lang=EN-US>P</SPAN><SPAN style="FONT-FAMILY: 宋体">为正、</SPAN><SPAN 
            lang=EN-US>N</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">为负）很小时（锗管小于</SPAN><SPAN 
            lang=EN-US>0.1</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">伏，硅管小于</SPAN><SPAN 
            lang=EN-US>0.5</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">伏），管子不导通处于</SPAN><SPAN 
            lang=EN-US>“</SPAN><SPAN style="FONT-FAMILY: 宋体">死区</SPAN><SPAN 
            lang=EN-US>”</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">状态，当正向电压起过一定数值后，管子才导通，电压再稍微增大，电流急剧暗加（见曲线</SPAN><SPAN 
            lang=EN-US>I</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">段）。不同材料的二极管，起始电压不同，硅管为</SPAN><SPAN 
            lang=EN-US>0.5-.7</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">伏左右，锗管为</SPAN><SPAN 
            lang=EN-US>0.1-0.3</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">左右。</SPAN><BR><SPAN 
            style="FONT-FAMILY: 宋体">（</SPAN><SPAN lang=EN-US 
            style="COLOR: blue">2</SPAN><SPAN 
            style="COLOR: blue; FONT-FAMILY: 宋体; Times: ">）反向特性</SPAN><BR><SPAN 
            style="FONT-FAMILY: 宋体">　　二极管两端加上反向电压时，反向电流很小，当反向电压逐渐增加时，反向电流基本保持不变，这时的电流称为反向饱和电流（见曲线</SPAN><SPAN 
            lang=EN-US>II</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">段）。不同材料的二极管，反向电流大小不同，硅管约为</SPAN><SPAN 
            lang=EN-US>1</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">微安到几十微安，锗管则可高达数百微安，另外，反向电流受温度变化的影响很大，锗管的稳定性比硅管差。</SPAN><BR><SPAN 
            style="FONT-FAMILY: 宋体">（</SPAN><SPAN lang=EN-US 
            style="COLOR: blue">3</SPAN><SPAN 
            style="COLOR: blue; FONT-FAMILY: 宋体; Times: ">）击穿特性</SPAN><BR><SPAN 
            style="FONT-FAMILY: 宋体">　　当反向电压增加到某一数值时，反向电流急剧增大，这种现象称为反向击穿（见曲线</SPAN><SPAN 
            lang=EN-US>III</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">）。这时的反向电压称为反向击穿电压，不同结构、工艺和材料制成的管子，其反向击穿电压值差异很大，可由</SPAN><SPAN 
            lang=EN-US>1</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">伏到几百伏，甚至高达数千伏。</SPAN><BR><SPAN 
            style="FONT-FAMILY: 宋体">　　（</SPAN><SPAN lang=EN-US 
            style="COLOR: blue">4</SPAN><SPAN 
            style="COLOR: blue; FONT-FAMILY: 宋体; Times: ">）频率特性</SPAN><BR><SPAN 
            style="FONT-FAMILY: 宋体">由于结电容的存在，当频率高到某一程度时，容抗小到使</SPAN><SPAN 
            lang=EN-US>PN</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">结短路。导致二极管失去单向导电性，不能工作，</SPAN><SPAN 
            lang=EN-US>PN</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">结面积越大，结电容也越大，越不能在高频情况下工作。</SPAN><SPAN 
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      <P class=MsoNormal align=center><SPAN lang=EN-US>&nbsp;<A 
      href="http://league.ysu.edu.cn/wuxie/dzjc/ejg.asp#top"><SPAN 
      style="FONT-FAMILY: 宋体">返回顶部</SPAN></A> </SPAN></P>
      <P class=titleb><A name=4>二、二极管检测方法</A></P>
      <P class=MsoNormal style="LINE-HEIGHT: 15pt"><STRONG>1.普通二极管的检测 
      </STRONG><BR><SPAN 
      style="FONT-FAMILY: 宋体">　　二极管的极性通常在管壳上注有标记，如无标记，可用万用表电阻档测量其正反向电阻来判断（一般用</SPAN><SPAN 
      lang=EN-US>R×100</SPAN><SPAN style="FONT-FAMILY: 宋体">或</SPAN><SPAN 
      lang=EN-US>×1K</SPAN><SPAN 
      style="FONT-FAMILY: 宋体">档）具体方法如表一。<BR></SPAN><SPAN 
      style="FONT-FAMILY: 宋体">表一</SPAN><SPAN lang=EN-US 
      style="COLOR: black; FONT-FAMILY: 宋体"> </SPAN><SPAN 
      style="FONT-FAMILY: 宋体">二极管简易测试方法</SPAN></P>
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            <P class=MsoNormal style="LINE-HEIGHT: 15pt" align=center><FONT 
            color=#990000><SPAN style="FONT-FAMILY: 宋体">项目</SPAN><SPAN 
            lang=EN-US style="COLOR: black; FONT-FAMILY: 宋体"> 
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          <TD width="41%" bgColor=white bord="1">
            <P class=MsoNormal style="LINE-HEIGHT: 15pt" align=center><FONT 
            color=#990000><SPAN 
style="FONT-FAMILY: 宋体">正向电阻</SPAN></FONT></P></TD>
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            <P class=MsoNormal style="LINE-HEIGHT: 15pt" align=center><FONT 
            color=#990000><SPAN 
        style="FONT-FAMILY: 宋体">反向电阻</SPAN></FONT></P></TD></TR>
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          <TD width="10%" bgColor=white>
            <P class=MsoNormal style="LINE-HEIGHT: 15pt"><FONT 
            color=#006600><SPAN style="FONT-FAMILY: 宋体">测试方法</SPAN><SPAN 
            lang=EN-US style="COLOR: black; FONT-FAMILY: 宋体"> 
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          <TD width="41%" bgColor=white>
            <P class=MsoNormal style="LINE-HEIGHT: 15pt; TEXT-ALIGN: center" 
            align=center><SPAN lang=EN-US><IMG height=95 
            src="电子基础2.files/diode.8.gif" width=139 border=0 
            v:shapes="_x0000_i1032"></SPAN><SPAN lang=EN-US 
            style="COLOR: black; FONT-FAMILY: 宋体"> </SPAN></P></TD>
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            <P class=MsoNormal style="LINE-HEIGHT: 15pt; TEXT-ALIGN: center" 
            align=center><SPAN lang=EN-US><IMG height=111 
            src="电子基础2.files/diode.9.gif" width=132 border=0 
            v:shapes="_x0000_i1033"></SPAN><SPAN lang=EN-US 
            style="COLOR: black; FONT-FAMILY: 宋体"> </SPAN></P></TD></TR>
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            <P class=MsoNormal style="LINE-HEIGHT: 15pt"><FONT 
            color=#006600><SPAN style="FONT-FAMILY: 宋体">测试情况</SPAN><SPAN 
            lang=EN-US style="COLOR: black; FONT-FAMILY: 宋体"> 
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            <P class=MsoNormal style="LINE-HEIGHT: 15pt"><SPAN 
            style="FONT-FAMILY: 宋体">硅管：表针指示位置在中间或中间偏右一点；锗管：表针指示在右端靠近满刻度的地方（如图所示）表明管子正向特性是好的。</SPAN><BR><SPAN 
            style="FONT-FAMILY: 宋体">如果表针在左端不动，则管子内部已经断路</SPAN><SPAN lang=EN-US 
            style="COLOR: black; FONT-FAMILY: 宋体"> </SPAN></P></TD>
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            <P class=MsoNormal style="LINE-HEIGHT: 15pt"><SPAN 
            style="FONT-FAMILY: 宋体">硅管：表针在左端基本不动，极靠近</SPAN><SPAN 
            lang=EN-US>OO</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">位置，锗管：表针从左端起动一点，但不应超过满刻度的</SPAN><SPAN 
            lang=EN-US>1/4</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">（如上图所示），则表明反向特性是好的，</SPAN><BR><SPAN 
            style="FONT-FAMILY: 宋体">如果表针指在</SPAN><SPAN lang=EN-US>0</SPAN><SPAN 
            style="FONT-FAMILY: 宋体">位，则管子内部已短路</SPAN><SPAN lang=EN-US 
            style="COLOR: black; FONT-FAMILY: 宋体"> 
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      <P class=MsoNormal 
      style="WORD-BREAK: break-all; LINE-HEIGHT: 130%"><STRONG>2.普通发光二极管的检测</STRONG><BR><SPAN 
      style="COLOR: black; LINE-HEIGHT: 130%; FONT-FAMILY: 宋体; Times: ">