| 摘要 |
PURPOSE:To hold high input impedance even in case of a power failure by providing diodes between a power source and positive and negative power terminals of a C-MOS analog switch with input terminals, and between respective inputs and a negative power terminal. CONSTITUTION:Diodes D1 and D2 are interposed forward between a positive power source VP and the positive power terminal 11 of a C-MOS IC analog switch 10 having inputs IN1 and IN2, and outputs OUT1 and OUT2, and between a negative power source VN and a negative power terminal 12. Further, Schottky diodes SD1 and SD2 are interposed having cathodes connected to the inputs IN1 and IN2 and anodes connected to the terminal 12. Consequently, when an input has a positive potential in case of a power failure, abnormal currents flowing from the sources to the power sources are cut off by the diodes D1 and D2, and a parasitic transistor (TR) formed in the C-MOS is turned off through the diodes SD1 and SD2 to prevent the generation of an abnormal current flowing between sources, thus holding high input impedance even in case of a power failure. |
