三级管电路简介（一）

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                    <section><section powered-by="gulangu"><section><section><p><img src="image/20201019/86195b02eb2bb22c4aa2cb0edbb7d742_1.gif" /></p></section></section></section><section powered-by="gulangu"><section><section> <section> <section powered-by="gulangu"><section><section><p>三极管的主要特性</p></section></section></section> </section> </section></section></section><section powered-by="gulangu"><section><section><p>1、电流放大和控制特性，及Ic=βIb、Ie=Ib+Ic、Ie﹥Ic﹥﹥Ib。</p><p>2、开关特性，三极管有截止、放大、饱和三个工作状态。</p><p>3、阻抗特性：三极管集电极、发射极之间的内阻是受Ib控制的，电流Ib愈大其内阻愈小，反之则愈大。</p></section></section></section><section powered-by="gulangu"><section><section> <section> <section powered-by="gulangu"><section><section><p>三极管的主要作用</p></section></section></section> </section> </section></section></section><section powered-by="gulangu"><section><section><p>1、放大作用：三极管能放大信号，可以构成具有各种用途的放大器。</p><p>2、开关作用：利用三级管的开关特性，可以构成电子开关电路。</p><p>3、恒流源作用，常用于集成电路的内电路</p><p>4、与其它元器件配合可以构成各种形式的振荡电路、控制电路等。</p></section></section></section><section powered-by="gulangu"><section><section> <section> <section powered-by="gulangu"><section><section><p>发射极放大器电路</p></section></section></section> </section> </section></section></section><section powered-by="gulangu"><section><section><p><img src="image/20201019/2e01d432aa80abccee61512a60815054_2.jpg" /></p></section></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; Vi为输入信号，Vo为输出信号。R1、R2构成分压式偏置电路，给T1管基极以合适的静态工作电流。</p><p>&nbsp; &nbsp; &nbsp; &nbsp;输入信号Vi经T1管基极→发射极→R4→地，构成输入回路，输出信号Vo经T1管集电极→发射极→R4→地，故称之为“共发射极电路”。</p><p>&nbsp; &nbsp; &nbsp; &nbsp;R3为T1管集电极负载电阻，作用是将T1管集电极电流转换成集电极电压，以便以信号电压形式传输给下一级电路。R4为发射电阻，它的作用有多种，主要是提供负反馈。R4具有交流和直流负反馈作用，交流负反馈可以改善信号的质量，直流负反馈可以稳定TI管的工作。</p><p>&nbsp; &nbsp; &nbsp; &nbsp;共发射极电路具有倒相作用，即输入信号电压Vi增大时，输出信号电压Vo为减小；反子，Vi减小，Vo则增大。因为，当Vi增大，具有Ib增大，Ic增大,Vc减小（Vc=+V-Ic*R3）。</p><p>&nbsp; &nbsp; &nbsp; &nbsp;共发射极电路的另一个特性是具有电流和电压放大作用。即当输入Ib时，T1管有Ic，Ic=βIb，有放大作用。具有电压放大作用可以这么理解：当Ib是由Vi产生的，很小的Vi便能产生Ib。Vo是由Ic通过R3获得的，只要R3足够大，Ic﹥﹥Ib，所以有Vo﹥﹥Vi，可见具有电压放大作用，且具有Vi、Vo反相的特性。</p><p>&nbsp; &nbsp; &nbsp; Vc=+V-Ic*R3可知，Vc的大小与R3的大小有关，对于交流信号而言，集电极输出电流ic在R3上的压降为交流信号输出电压，可见在一定范围适当加大R3的阻值可获得较大的集电极交流信号输出电压，这意味着加大R3可以使T1管增益变大。</p></section></section></section><section powered-by="gulangu"><section><section><p><br  /></p></section></section></section><section powered-by="gulangu"><section><section> <section powered-by="gulangu"><section><section><p>欢</p></section></section></section> </section><section> <section powered-by="gulangu"><section><section><p>迎</p></section></section></section> </section><section> <section powered-by="gulangu"><section><section><p>关</p></section></section></section> </section><section> <section powered-by="gulangu"><section><section><p>注</p></section></section></section> </section></section></section><section powered-by="gulangu"><section><section><p><br  /></p></section></section></section><section powered-by="gulangu"><section><section> <section powered-by="gulangu"><section><section><p><img src="image/20201019/ec3e080a8651c6e458e000cd6322b2b2_3.jpg" /></p></section></section></section> </section><section> <section powered-by="gulangu"><section><section> </section></section></section> </section><section> <section powered-by="gulangu"><section><section><p>关注我们</p><p>一起涨姿势！</p></section></section></section> </section></section></section></section>