| 摘要 |
Variable attenuators (200, 400, 618, 620) and methods of their operation are provided. A variable attenuator (200, 400, 618, 620) includes first and second variable resistance circuits (210, 411, 250, 451) and multiple additional resistors (222, 223, 230, 231, 423, 424, 432, 433). The first variable resistance circuit (210, 411) has a plurality of current paths (212, 213, 214, 414, 415) coupled in parallel between input and output terminals (202, 405, 204, 406). A first current path (213, 415) includes two first resistors (222, 223, 423, 424) coupled in series between the input and output terminals, and a switch (230, 432), which has a channel coupled across one of the two first resistors. The multiple additional resistors include second and third resistors (230, 432, 231, 433). The second resistor (230, 432) is coupled between the input terminal and an intermediate node (206, 408). The third resistor (231, 433) is coupled between the output terminal and the intermediate node (206, 408). The second variable resistance circuit (250, 451) is coupled between the intermediate node and a voltage reference terminal (270, 470). The level of attenuation provided by the attenuator is controlled by a switch control circuit (300, 500) based on a digital input. |
