| 摘要 |
An AGC circuit includes an amplifier, a first detector, a pulse generator, a second detector, a switching circuit, and a gain controller. The amplification factor of the amplifier for an input signal is controlled by a gain control voltage. The first detector detects the output level of the amplifier. The pulse generator generates a variable-width pulse signal on the basis of an output from the first detector. The second detector detects the presence/absence of an input signal. The switching circuit switches between an output from the pulse generator and an output from the first detector and outputs the switched output in accordance with a detection output from the second detector. The gain controller outputs the gain control voltage to the amplifier on the basis of an output from the switching circuit. Upon switching an input signal and turning on the power supply, the pulse generator outputs a pulse signal having a predetermined pulse width to the switching circuit to temporarily set the gain control voltage of the amplifier near the operating point.
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