| 摘要 |
PURPOSE:To expand the applicability of an external device possible to be connected to an input terminal, by changing an input threshold voltage by changing the combined conductance of a first and a second transistors connected in parallel. CONSTITUTION:An N-channel transistor Q3 is connected in parallel with an N-channel transistor Q2, and the base is connected to the input terminal 1 similarly as the transistor Q2. Also, both electrodes, the drain and the source of an N-channel transistor Q4 are connected between the drains of the transistors Q2 and Q3, and a control signal S is impressed on the gate. When the control signal S is set at an L level, the transistor Q4 is turned OFF, and the transistor Q3 is cut off electrically from an inverter circuit. When the control signal S is set at an H level, the transistor 04 is turned ON, and the transistor Q3 is connected in parallel with the transistor Q2.
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