| 摘要 |
PURPOSE:To prevent an analog switch which is in an off state from turning on in response to an input voltage, and to realize normal switch functions, by using a parasitic ROM having a high threshold voltage for exercising control over a switching signal. CONSTITUTION:An analog and digital combined LSI is used to form an analog switch for inputting an analog voltage to an LSI. For this purpose, a voltage as a reverse bias to an input voltage range is applied to the same substrate with an MOS transistor (TR) 24 for the analog switch. For exercising control over the gate terminal of this MOSTR24, the drain and souce of a parasitic MOSTR26 applied at the substrate and souce with a voltage equal to the substrate voltage are connected. An active MOSTR applied with the substrate voltage at the substrate is combined and either MOSTR is turned on and off to decide on the on-off state of the analog switch 27. |
