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| 一、场效应管直流偏置电路 |
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场效应管的单电源直流偏置电路有两种： |
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1.
只能用于结型和耗尽型MOS管的自给偏置电路；
2. 可用于各种场效应管的分压式偏置电路。
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1.自给偏压电路 |
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（1）图解法 |
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根据图中电路的输出回路列出直流负载线方程： |
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再根据输入回路列出直流负载线方程： |
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（2）计算法（列方程组求解） |
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式中的IDSS和UP可以从特性曲线上求出，或者从产品手册上查到。 |
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自给偏置电压的缺点是： |
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当为提高稳定工作点的能力而增大Rs时，IDQ减小，（Q下移），使gm和Au随之减少。 |
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2.分压式自偏压电路 |
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将转移特性的近似函数式与根据电路列出的直流电压方程联立，就可求解静态工作点。 |
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分压式自偏压电路可通过调整电阻分压比来改善静态工作点 |
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