| 摘要 |
PROBLEM TO BE SOLVED: To obtain an MOS transistor switch which turns ON and OFF signals between 0 level and the source voltage level by comparing voltages at the terminals of the switch with its source voltage and allowing an operation with the highest voltage. SOLUTION: Voltage comparing circuits 6 and 7 output higher voltages V6 and V7 between a source voltage VDD and terminal VA and VB of a PMOS transistor. A voltage comparing circuit 5 output higher voltage VPW between the output voltages V6 and V7 of the comparing circuit 6 and 7. The voltage VPW is higher that the voltage VA, VB, and VDD and with this voltage, voltage comparing and detecting circuits 1 and 3, a logic gate 2, voltage comparing circuit 5, 6, and 7, and the PMOS transistor 4 operate. When the voltage VA and VB are higher that the source voltage VDD, the detecting circuits 1 and 3 output L-level signals and the PMOS transistor 4 turns OFF. The switch 4 operates with the highest voltages, so no current flows from terminals A and B to the power source. |
