| 摘要 |
PROBLEM TO BE SOLVED: To securely shut down signal transmission between a first and a second terminals, when supply voltage is not supplied. SOLUTION: An analog switch circuit comprises a first and a second terminals I/O and O/I for bidirectional signal input and output, a PMOS transistor P1 and an NMOS transistor N1 connected in parallel between the first and the second terminals I/O and O/I, a control circuit 1 for controlling turn-on and turn-off of these transistors, and diodes D1-D6. In a N well NW1, the PMOS transistor P1 as well as the diodes D5 and D6 for setting of substrate potential of the transistor are formed. In a N well NW2 separate from the N well NW1, the diodes D3 and D4 for delivering voltage surge in the first and the second terminals I/O and O/I to a NAND gate G1 are formed. According to the arrangement, the size of the N wells can considerably be reduced from conventional one, and voltage surge in the first and the second terminals I/O and O/I can be quickly transmitted to a power terminal of the NAND gate G1. COPYRIGHT: (C)2005,JPO&NCIPI
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