Voltage controlled attenuator

摘要

A voltage controlled attenuator having extremely wide dynamic range and having low distortion is achieved by limiting the current density in each unit area of the transistors to minimize the current noise and by utilizing high current sources to minimize the noise voltage. A pair of compound gain cells having low current densities are each directly fed by a linearized current source. The gain cells are controlled by a single gain control voltage and feed a pair of linearized buffer amplifiers for minimizing loading on the gain cells. The output of the buffer amplifiers feed a differential output amplifier for generating an output signal that eliminates the effect of the control voltage in the output signal and any DC shift caused by changes in control voltage and nulls remaining distortion products.