| 摘要 |
PURPOSE:To discriminate whether the level of a DC input voltage becomes a prescribed level or not by lighting of a light emitting diode. CONSTITUTION:When a DC input voltage Vin is within a range SL21-SL22, the potential of the output terminal of a Schmitt trigger circuit A21 is about -VEE, and a potential difference of about (VCC+VEE) is applied to both ends of the series connection of a light emitting diode D and a resistance R because the potential of a Schmitt trigger circuit A22 is VCC, and the light emitting diode D is lit. When the DC input voltage Vin is equal to or higher than (SL21 +SL22), potentials of output terminals of Schmitt trigger circuits A21 and A22 are about -VEE together and no potential difference is generated in both ends of the light emitting diode D, and the diode D is not lit. |
