| 摘要 |
PROBLEM TO BE SOLVED: To provide an automatic gain control (AGC) circuit which can be integrally formed on a semiconductor substrate. SOLUTION: The AGC circuit 17 controls a gain of an intermediate frequency amplifier circuit 15 so that the average level of an output signal (audio signal) of an AM detection circuit 16 may be approximately constant. The circuit 17 includes a time constant circuit 100. The circuit 100 is provided with a charging circuit for intermittently charging a capacitor and a discharging circuit for intermittently discharging the capacitor. With this constitution, by intermittently charging and discharging the capacitor having small capacitance, a large time constant is set.
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