| 摘要 |
PURPOSE:To migigate masking, by discharging charges stored in a storage circuit, only when no effective signal exists in the output of an external noise detecting circuit and conducting a gate circuit only when the signal exists in the output. CONSTITUTION:Even if an output level of an external noise detecting circuit 12 intermittently decreases and an output level of an integration circuit 13 is lowered, since the output level of an integration circuit 14 drops more slowly than the output level of the circuit 13, before the output level of the circuit 13 drops remarkably, the output level of the circuit 14 is larger than that of the circuit 13, and a gate circuit 17 is made nonconductive during this period, the output of the circuit 13 just before the output levels of the circuits 13 and 14 cross over is stored in a storage circuit 18, allowing to mitigate masking. If the output of the circuit 12 is temporarily at zero potential, the charges stored in the circuit 18 are discharged via a gate circuit 20, but this discharge time constant is suitably selected, allowing to mitigate masking similarly, without dropping the output of the circuit 18. |
