| 摘要 |
PURPOSE:To detect reference voltage including earth voltage stably and highly accurately by using a pair of voltage dividing circuits practically having the same constitution as an input circuit and a reference voltage circuit. CONSTITUTION:When input voltage VIN crosses zero voltage from negative to possitive voltage, the impedance of depression IGFETQ2 in an input circuit 1 is reduced lower than that of a depression IGFETQ4 in a reference voltage circuit 2, the output level of an enhancement FETQ12 is increased and the output level of an enhancement FETQ14 is reduced. Consequently, an FETQ12 in an output buffer circuit 4 is turned on, an FETQ17 is turned off, an FETQ19 is turned on, and output voltage VOUT is reduced from the high level to the low level close to VSS=0V, so that the earth voltage can be detected highly accurately even at a crossing moment. |
