| 摘要 |
PROBLEM TO BE SOLVED: To stabilize the operation of a voltage limiter circuit by including a MOS capacitor whose threshold voltage is negative in an internal voltage generating circuit generating internal voltages by receiving an operating power source voltage. SOLUTION: In drive circuits 7a, 7b, when wirings of outputs of the circuits intersect a wiring 12a, a feedback circuit is generated via the parasitic capacitance CC3 between wirings and operations of the circuits becomes unstable. In order to prevent this unstableness, the gain of a loop is made to be sufficiently small by inserting capacitors CR1 , CR2 whose capacitances are sufficiently larger than parastic capacitances CC1 to CC3 . Capacitors to be used in here are formed between gates and a substrate surface across a gate insulating film and large capacitances can be obtained with relatively small areas by using a thin gate insulating film as a capacitor insulating film. Since there are wells under the gates, the threshold voltage of the capacitors is negative and capacitances of the capacitors becomes roughly constant as long as a voltage of one direction is applied on them so that sides of gates become positive. |
