System for logarithmically controlling multiple variable gain amplifiers

摘要

A system for producing a control signal to a plurality of amplifiers sections to vary the gain of each one of the plurality of amplifier sections as a linear natural logarithmic function of an input gain control signal. The system includes a master circuit for producing a pair of currents with a ratio proportional to the linear natural logarithmic function of the input gain signal and a differential voltage. Each one of the amplifier sections includes: a replica of a portion of the master circuit fed by the produced differential voltage for producing a pair of currents produced in the master circuit; and an amplifier fed by the produced replicated currents, such amplifier having a gain proportional to the ratio of such replicated currents.