Variable attenuator for attenuating gain of analog signal in accordance with digital signal

摘要

A variable attenuator has a plurality of attenuation resistor units, a plurality of switching units, and a plurality of impedance compensation resistor units. The attenuation resistor units are connected in series for attenuating an input signal, and the switching units are provided for the attenuation resistor units. One of the switching units are selected in accordance with a digital control signal supplied from an external source. Each of the impedance compensation resistor units is connected in series with the respective switching units to compensate an output impedance to a specific value regardless of the state of the switching units. Therefore, the variable attenuator of the present invention can correctly control the level of an analog signal by a digital signal.