| 摘要 |
PROBLEM TO BE SOLVED: To provide a protecting circuit for a MOS device, that enables the MOS device to operate normally even when an input voltage exceeding the driving voltage of the MOS device is input while suppressing an increase in chip size. SOLUTION: In the protecting circuit 10, a ground level shifting circuit 10a sets a virtual ground Vgnd which is lower than the input minimum voltage of an input voltage Vin and can set the potential of a driving voltage Vdd nearly equal to the potential of a battery voltage VB to the ground Gnd of the driving voltage Vdd. Consequently, even when the input maximum voltage exceeds the driving voltage Vdd for a ground E of the battery voltage VB and the input voltage Vin lower than the battery voltage VB is input to the CMOS device of a CMOS circuit 50, the input voltage Vin can be input within the input permissible voltage width of the CMOS device. The CMOS device is therefore enabled to operate normally without using the CMOS device having high breakdown voltage, and while an increase in chip size is suppressed, the CMOS device can operate normally. COPYRIGHT: (C)2008,JPO&INPIT
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