VARIABLE GAIN CMOS AMPLIFIER

摘要

A variable gain amplifier includes an input transconductor (10) having a transconductance that is variable in response to a first control signal (Ci), an output circuit (20) having a transresistance that is variable in response to the second control signal (Co) and a gain controller (30) responsive to a gain control signal x for providing the first and second control signals to the input transconductor and the output circuit. The amplifier has a voltage gain equal to the product of the transconductance and the transresistance. When the first control signal is a function (1 + x) of the gain control signal and the second control signal is a function (1 - x) of the gain control signal, the voltage gain of the amplifier is approximately an exponential function of the gain control signal.