Patent ID: 7362172

Claim:
A variable gain circuit, comprising: a first amplifier with high gain having a first amplifier input and a first amplifier output, and being gain-controlled by a first gain control signal; and a second amplifier with low gain having a second amplifier input and a second amplifier output, and being gain-controlled by a second gain control signal, wherein direction of a gain change of the first amplifier with respect to a change of the first gain control signal, and direction of a gain change of the second amplifier with respect to a change of the second gain control signal are set in reverse to each other, and the first gain control signal and the second gain control signal are in common use, wherein an input signal is supplied in common to the first and the second amplifiers by coupling the first amplifier input and the second amplifier input with each other, and the output signal of the first amplifier and the output signal of the second amplifier are additionally combined by coupling the first amplifier output and the second amplifier output with each other, and wherein the first amplifier has a function to turn on and off an output in response to a mode switching signal.