| 摘要 |
PURPOSE:To suppress an unnecessary variation component from being contained in an output signal by making an integrator have a time constant switching function, and a stop and restart function of an integral operation. CONSTITUTION:An integrator 25 is made to have a time constant switching function, and a stop and restart function of an integral operation, and when turning on a power source and when switching a channel, a value of an integral time constant is set small. In this state, an AGC operating state and a gain varying state of a signal which becomes a controlled system are monitored by a detector 26, and in case when stability of the AGC operating state has been confirmed by monitoring an output data variation of the integrator 25, the integral operation is stopped temporarily, also a time constant is switched to a large value, and thereafter, monitoring of a gain variation of the signal which becomes a controlled system is continued. In case when this gain variation has exceeded a prescribed range, the integral operation is started again.
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