| 摘要 |
<p>A step attenuator (320) with constant input capacitance is disclosed. In an exemplary design, an apparatus includes a step attenuator (320) having a constant input capacitance for different amounts of attenuation. The step attenuator (320) receives an input signal (Vin), provides a variable amount of attenuation for the input signal, and provides an output signal (Vout). The step attenuator (320) may include a plurality of attenuator sections (340a - 340k) coupled in series. Each attenuator section (340a - 340k) may include a plurality of capacitors (342a - 342k; 346a - 346k) connected in series and shunt configuration. Switches (344a - 344k; 348a - 348k) are respectively connected in series with the shunt capacitors (342a - 342k) and in parallel with the series ones (346a - 346k). At least one of the plurality of attenuator sections (340a - 340k) is selected to obtain a selected amount of attenuation for the step attenuator. An attenuator section (340a - 340k) may provide a predetermined amount of attenuation or a variable amount of attenuation when selected. The apparatus further includes a power detector that receives and determines the power of the output signal from the step attenuator.</p> |
