| 摘要 |
PURPOSE:To obtain an input circuit resistant to noise and possible for sure operation by providing a hysteresis voltage adjusting circuit whose hysteresis voltage value is decreased when a power supply voltage is fluctuated from the standard voltage. CONSTITUTION:A power supply voltage circuit 3 monitors a voltage value of a power supply 2 in an input circuit and a hysteresis voltage adjusting circuit 4 outputs a signal 5 in response to the value. Thus, even if a hysteresis voltage VH of the Schmitt trigger circuit 1 is set large, a VH is controlled by the hysteresis voltage adjusting circuit 4 at the fluctuation of the power voltage and becomes smaller so that the input level satisfies the standard. Then the circuit above is resistant to noise at normal operation and activated surely even at the fluctuation. |
