| 摘要 |
PROBLEM TO BE SOLVED: To provide an input output driver circuit that has both high level voltage tolerance and extensibility and has only two power supply pins. SOLUTION: The input output driver circuit employs two PMOS switching transistors (T1A, T1B) between an output line (30) of the circuit and an output power terminal (42) instead of one transistor to provide a buffer interface between a functional digital circuit (14) and a common bus (18) for other digital circuits and uses only the two required power pins (38, 42) while attaining high level voltage tolerance and the extensibility. Applying a voltage of an output power supply (40) to one-side gates of the transistors and the output line voltage to the other gates switches off the transistors. Thus, at least either of the transistors is surely turned off as required at maximum independently of whether or not the output line voltage exceeds the output power level.
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