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<h1 id="数模模数转换">数/模、模/数转换</h1>
<h2 id="数模转换">数/模转换</h2>
<p>把输入的数字信号转换成与之成正比的输出模拟电压或电流。 <br>
转换方法为按权展开法，把输入每一位按其对应权大小转换为相应的模拟量，再利用求和运算放大器相加。 <br>
输入数字量为1时的输出电压称为DAC的单位量化电压。显然，可输出的最大电压为<span class="MathJax_Preview" style="color: inherit; display: none;"></span><span class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>u</mi><mrow class="MJX-TeXAtom-ORD"><mi>O</mi><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub><mo>=</mo><mo stretchy="false">(</mo><msup><mn>2</mn><mi>n</mi></msup><mo>&#x2212;</mo><mn>1</mn><mo stretchy="false">)</mo><msub><mi>U</mi><mi mathvariant="normal">&#x0394;</mi></msub></math>" id="MathJax-Element-1-Frame" role="presentation" style="position: relative;" tabindex="0"><nobr aria-hidden="true"><span class="math" id="MathJax-Span-1" style="width: 10.523em; display: inline-block;"><span style="display: inline-block; position: relative; width: 8.753em; height: 0px; font-size: 120%;"><span style="position: absolute; clip: rect(1.253em, 1008.75em, 2.555em, -999.997em); top: -2.133em; left: 0em;"><span class="mrow" id="MathJax-Span-2"><span class="msubsup" id="MathJax-Span-3"><span style="display: inline-block; position: relative; width: 2.607em; height: 0px;"><span style="position: absolute; clip: rect(3.44em, 1000.58em, 4.169em, -999.997em); top: -4.008em; left: 0em;"><span class="mi" id="MathJax-Span-4" style="font-family: MathJax_Math-italic;">u</span><span style="display: inline-block; width: 0px; height: 4.013em;"></span></span><span style="position: absolute; top: -3.852em; left: 0.576em;"><span class="texatom" id="MathJax-Span-5"><span class="mrow" id="MathJax-Span-6"><span class="mi" id="MathJax-Span-7" style="font-size: 70.7%; font-family: MathJax_Math-italic;">O</span><span class="mi" id="MathJax-Span-8" style="font-size: 70.7%; font-family: MathJax_Math-italic;">m</span><span class="mi" id="MathJax-Span-9" style="font-size: 70.7%; font-family: MathJax_Math-italic;">a</span><span class="mi" id="MathJax-Span-10" style="font-size: 70.7%; font-family: MathJax_Math-italic;">x</span></span></span><span style="display: inline-block; width: 0px; height: 4.013em;"></span></span></span></span><span class="mo" id="MathJax-Span-11" style="font-family: MathJax_Main; padding-left: 0.263em;">=</span><span class="mo" id="MathJax-Span-12" style="font-family: MathJax_Main; padding-left: 0.263em;">(</span><span class="msubsup" id="MathJax-Span-13"><span style="display: inline-block; position: relative; width: 0.992em; height: 0px;"><span style="position: absolute; clip: rect(3.18em, 1000.47em, 4.169em, -999.997em); top: -4.008em; left: 0em;"><span class="mn" id="MathJax-Span-14" style="font-family: MathJax_Main;">2</span><span style="display: inline-block; width: 0px; height: 4.013em;"></span></span><span style="position: absolute; top: -4.424em; left: 0.523em;"><span class="mi" id="MathJax-Span-15" style="font-size: 70.7%; font-family: MathJax_Math-italic;">n</span><span style="display: inline-block; width: 0px; height: 4.013em;"></span></span></span></span><span class="mo" id="MathJax-Span-16" style="font-family: MathJax_Main; padding-left: 0.211em;"></span><span class="mn" id="MathJax-Span-17" style="font-family: MathJax_Main; padding-left: 0.211em;">1</span><span class="mo" id="MathJax-Span-18" style="font-family: MathJax_Main;">)</span><span class="msubsup" id="MathJax-Span-19"><span style="display: inline-block; position: relative; width: 1.357em; height: 0px;"><span style="position: absolute; clip: rect(3.18em, 1000.78em, 4.169em, -999.997em); top: -4.008em; left: 0em;"><span class="mi" id="MathJax-Span-20" style="font-family: MathJax_Math-italic;">U<span style="display: inline-block; overflow: hidden; height: 1px; width: 0.107em;"></span></span><span style="display: inline-block; width: 0px; height: 4.013em;"></span></span><span style="position: absolute; top: -3.852em; left: 0.68em;"><span class="mi" id="MathJax-Span-21" style="font-size: 70.7%; font-family: MathJax_Main;">Δ</span><span style="display: inline-block; width: 0px; height: 4.013em;"></span></span></span></span></span><span style="display: inline-block; width: 0px; height: 2.138em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.372em; border-left: 0px solid; width: 0px; height: 1.316em;"></span></span></nobr><span class="MJX_Assistive_MathML" role="presentation"><math><msub><mi>u</mi><mrow class="MJX-TeXAtom-ORD"><mi>O</mi><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub><mo>=</mo><mo stretchy="false">(</mo><msup><mn>2</mn><mi>n</mi></msup><mo></mo><mn>1</mn><mo stretchy="false">)</mo><msub><mi>U</mi><mi mathvariant="normal">Δ</mi></msub></math></span></span>。 <br>
多数集成DAC是电流输出型，需要在后面接一个反相比例运算放大器以实现电流电压的转换，才t得到模拟电 |
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