| 摘要 |
PURPOSE:To prevent an MOS transistor from being subjected to an effect due to a dispersion of the threshold value and an effect due to a shift of the threshold value, which generates during use of the MOS transistor, by a method wherein the potential generating circuit is set in an action state by an enable signal and the output potential thereof is shifted from the initial value to the prescribed amount. CONSTITUTION:The output of a negative potential generating circuit 34 is an earth potential and the respective threshold voltages of a transistor 32 for sensor and a transistor 30 for being controlled are one in the vicinity of 0.8V. The transistor 32 for sensor is turned to an ON state as its gate voltage Vx is 1.0V, and the negative potential generating circuit 34 receives an enable signal and outputs the prescribed negative potential. The respective threshold voltages are shifted to the positive side and attempt to become larger than 1.0V. At this time, however, the transisitor 32 for sensor is inverted to an OFF state, the negative potential generating circuit 34 ceases from receiving the enable signal and the output thereof is held for a constant hour. Shortly after that, the transistor 32 for sonsor is again turned into an ON state when the output of the negative potential generating circuit approaches the earth potential. By a repetition of such the action, the threshold voltage of the transistor 32 for sensor is held in the vicinity of the 1.0V of the gate voltage Vx thereof. |
