Amplifier circuit having gain control

摘要

An amplifier circuit comprises a variable gain amplifier for receiving an input signal which is to be amplified by the amplifier circuit with a variable gain. The variable gain is controlled by a control signal. The amplifier circuit also includes a constant gain amplifier for amplifying a signal outputted from the variable gain amplifier with a constant gain, and a gain control circuit responsive to a signal outputted from the constant gain amplifier so as to supply the control signal to the variable gain amplifier. The signal from the constant gain amplifier is outputted as an output signal of the amplifier circuit, and the gain control circuit generates the control signal during a time period in which a level of the output signal of the constant gain amplifier is higher than a reference level which is a predetermined value lower than a peak value of the output signal of the constant gain amplifier.