| 摘要 |
PURPOSE:To improve the control performance of a logic threshold voltage and a hysteresis voltage of the titled circuit and to attain the steep hysteresis characteristic by adding the 2nd control circuit controlling the potential of a signal internal output terminal using an external output terminal as an input source to a conventional Schmitt trigger circuit. CONSTITUTION:P-channel MOS transistors (TRs) 1,2 are turned on in the process that a signal input voltage VIN reaches a level V4a+Vt3, an H level is obtained at the signal internal output terminal 2a and an L level is obtained at a signal external output terminal 5a. Since P-channel MOS TRs 8, 18 are turned on even when the signal input voltage VIN exceeds the threshold voltage of an N-channel MOS TR 4 and reaches a value being a difference between a threshold voltage Vt1 of the TR 1 and a power voltage VDD, the signal internal output terminal 3a keeps the H level. When the signal input voltage VIN is higher than the voltage V4a of a connecting point 4a by the threshold voltage Vt3 of the N-channel MOS TR 3, the said TR 3 starts turning on.
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