<p><strong>1 二阶压控低通滤波器</strong></p>
<p>二阶压控低通滤波器电路如图所示，由R1、C1 及R2、C2 分别构成两个一阶低通滤波器，但C1 接输出端，引入电压正反馈，形成压控滤波器。</p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="6e6dfa29-0578-4611-87ce-b2c612145e00" src="/sites/default/files/inline-images/2_64.png" /></p>
<p><strong>(1) 传递函数</strong></p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="6dbd3bf5-e66e-4808-b902-8551e367aafc" src="/sites/default/files/inline-images/1_74.png" /></p>
<p><strong>(2) 频率特性</strong></p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="de6b1bb9-8f5e-47b8-a966-6688bb0968c2" src="/sites/default/files/inline-images/4_53.png" /></p>
<p>可见该低通滤波器特点是阻尼系数ζ 由电阻R1、R2，C1、C2 的比决定；而固有频率ω0与R1、R2、C1、C2 具体数值有关，即ω0与ζ 独立可调，互不影响。</p>
<p><strong>(3) 参数选择</strong></p>
<p>为方便参数匹配，考虑到标称电容种类较少，一般选择C1=C2=C。通过选择不同的R1、R2 满足特定的固有频率ω0 、ζ 。</p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="a7073f4c-c8d2-44ad-b04f-0980ba877ff9" src="/sites/default/files/inline-images/1_73.png" /></p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="27706036-4a4a-4054-abce-a2506a7141ed" src="/sites/default/files/inline-images/2_63.png" /></p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="5785a40e-7bfc-4272-b61d-f4a6279b5a94" src="/sites/default/files/inline-images/3_60.png" /></p>
<p><strong>2单位增益二阶压控低通滤波器</strong></p>
<p>对于二阶压控低通滤波器来说，当通带放大倍数Aup =1(单位增益)时，图所示电路变为图所示，其中RF=R1+R2。</p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="4834d128-deef-4203-a610-fa3ad95acee9" src="/sites/default/files/inline-images/1_72.png" /></p>
<p><strong>(1) 基本关系</strong></p>
<p><img alt="2" data-entity-type="file" data-entity-uuid="fdef320e-1a24-48fc-b628-5ebee41acbc8" src="/sites/default/files/inline-images/2_62.png" /></p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="a13377a5-a6f5-4224-9da8-147f6cafda02" src="/sites/default/files/inline-images/3_59.png" /></p>
<p><strong>(4) 参数选择</strong></p>
<p>在固有频率ω0 、阻尼系数ζ 已知情况下，设计步骤如下：</p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="4111cb3c-a3e8-45f3-ac4b-2db54ffdf17f" src="/sites/default/files/inline-images/1_71.png" /></p>
<p><strong>3二阶低通滤波器</strong></p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="c0eb99aa-5535-4fdc-bb67-412b4044dd2d" src="/sites/default/files/inline-images/6_34.png" /></p>
<p><strong>(1) 传递函数</strong></p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="e9dd58db-31c4-4f11-9d32-af750276ad8f" src="/sites/default/files/inline-images/5_39.png" /></p>
<p><strong>(2) 频率特性</strong></p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="4abca851-0654-4f12-99e3-2719f8459ed1" src="/sites/default/files/inline-images/4_52.png" /></p>
<p><strong>4无限增益多路反馈低通滤波器</strong></p>
<p><img alt="2" data-entity-type="file" data-entity-uuid="cc29fde4-e9dd-4fc3-8285-b913c8820b55" src="/sites/default/files/inline-images/3_58.png" /></p>
<p><strong>(1) 传递函数</strong></p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="cffb8925-07d0-4d55-b851-ee61f9d55069" src="/sites/default/files/inline-images/2_61.png" /></p>
<p><strong>(2) 频率特性</strong></p>
<p><img alt="1" data-entity-type="file" data-entity-uuid="b31a17ef-488d-4a5c-b57f-ea87bb81de47" src="/sites/default/files/inline-images/1_70.png" /></p>
<p>来源：<a href="https://mp.weixin.qq.com/s/0t7IZazMpAIxprhzNjxZUA">电子工程师笔记</a></p>