Logarithmically linearly controlled variable gain amplifier

摘要

A variable gain amplifier of the logarithmically linear type comprises a divider for dividing a signal applied to the input terminal of the amplifier by a gain control signal. The output of the divider is applied to a first input of a subtractor, the second input of the subtractor being connected to receive the signal applied to the amplifier's input terminal to deliver a signal to the output terminal of the amplifier. The amplifier has an input-to-output characteristic given by (2n/x)-1 which is approximated to exp{2-x/(2n-2)}, where x represents the gain control signal.