Patent ID: 7821335

Claim:
A semiconductor integrated circuit comprising: a variable gain resistive feedback amplifier having a transistor for amplification, a load resistance, and a voltage follower for feedback, wherein a common terminal of an emitter or a source of the transistor for amplification is connected to a predetermined reference voltage, wherein an input signal is supplied to an input terminal of a base or gate of the transistor for amplification, wherein the load resistance is connected between an output terminal of a collector or drain of the transistor for amplification and a power supply voltage, wherein the output terminal of the transistor for amplification is connected with an input of the voltage follower for feedback, wherein a feedback resistance is connected between an output of the voltage follower for feedback and the input terminal of the transistor for amplification, wherein, in the variable gain resistive feedback amplifier, resistance values of the load resistance and feedback resistance are changed in response to a gain control signal in cooperation, wherein, when the load resistance is controlled to a high load resistance in response to the gain control signal setting the variable gain resistive feedback amplifier to a high gain, the feedback resistance is controlled to a high feedback resistance, and wherein, when the load resistance is controlled to a low load resistance, lower than the high load resistance, in response to the gain control signal setting the variable gain resistive feedback amplifier to a low gain, lower than the high gain, the feedback resistance is controlled to a low feedback resistance that is lower than the high feedback resistance.