Patent ID: 8618879

Claim:
A semiconductor device comprising a variable gain amplifier circuit for amplifying an input signal by a gain according to a control signal, the variable gain amplifier circuit including: an output node for outputting an amplified input signal; a plurality of amplifiers which are coupled in parallel with each other between the output node and a first reference node to which a first reference potential is provided and selectively assume an operating state in accordance with the control signal; and a detection circuit which detects the input signal and outputs a detection signal according to a magnitude of the detected input signal to each of the amplifiers, each of the amplifiers including: a first transistor which receives, at its control electrode, the input signal or a signal proportional to the input signal; a second transistor which is series-coupled to the first transistor between the first reference node and the output node; and a first bias circuit which applies a DC voltage of a magnitude according to the detection signal to a control electrode of the second transistor.