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1. 发明授权

US5453718A Differential amplifier for reducing input capacitance without deterorating noise characteristics 失效
标题翻译：用于降低输入电容的差分放大器，不会阻碍噪声特性
公开(公告)号：US5453718A
公开(公告)日：1995-09-26
申请号：US284122
申请日：1994-08-02
申请人： Katuyuki Kurokawa , Takehiko Umeyama , Masayasu Tanaka
发明人： Katuyuki Kurokawa , Takehiko Umeyama , Masayasu Tanaka
IPC分类号： H03F3/45
CPC分类号： H03F3/4521 , H03F3/45089 , H03F2203/45024 , H03F2203/45031 , H03F2203/45302 , H03F2203/45366 , H03F2203/45584 , H03F2203/45594 , H03F2203/45702
摘要： A differential amplifier (101) includes an input circuit (20), a bias circuit (31) and an output circuit (50). In the input circuit (20), when base potentials of transistors (Q1) and (Q2) change respectively by .DELTA.V and -.DELTA.V thereby changing current flowing through the transistors (Q1) and (Q2) by .DELTA.I and -.DELTA.I, respectively, base-emitter voltages of transistors (Q5) and (Q9) equally increase by .DELTA.V in the bias circuit (31). However, since a base potential of the transistor (Q5) is fixed, an emitter potential of the transistor (Q9) drops by 2.DELTA.V, decreasing a base potential of a transistor (Q4) by 2.DELTA.V. On the other hand, since a current flowing through the transistor (Q4) changes by -.DELTA.I, a base-emitter voltage of the transistor (Q4) accordingly falls by .DELTA.V. This reduces an emitter potential of the transistor (Q4), i.e., a collector potential of the transistor (Q2) by .DELTA.V, and hence, a base-emitter voltage of the transistor (Q2) stays unchanged. Thus, Miller effect is prevented and an input capacitance is reduced.
摘要翻译：差分放大器（101）包括输入电路（20），偏置电路（31）和输出电路（50）。在输入电路（20）中，当晶体管（Q1）和（Q2）的基极电位分别改变DELTA V和-TATA V，从而改变流过晶体管（Q1）和（Q2）的电流DELTA I和DELTA I 晶体管（Q5）和（Q9）的基极 - 发射极电压分别在偏置电路（31）中增加DELTA V. 然而，由于晶体管（Q5）的基极电位是固定的，所以晶体管（Q9）的发射极电位下降2VTAV，将晶体管（Q4）的基极电位降低2VTA。另一方面，由于流过晶体管（Q4）的电流改变了-ΔTA，所以晶体管（Q4）的基极 - 发射极电压相应地下降了DELTA V.这降低了晶体管（Q4）的发射极电位，即集电极电位（Q2）的晶体管（Q2）的晶体管（Q2）的基极 - 发射极电压保持不变。因此，可以防止米勒效应，降低输入电容。

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