| 摘要 |
PURPOSE:To reduce a consumed electric current in a substratepotential generation circuit by a method wherein a substrate potential is detected and the oscillation frequency of an oscillation circuit in the substrate-potential generation circuit is changed over by the value of the detected potential. CONSTITUTION:Since a substrate bias potential VSUB does not reach a substrate bias potential VSU'B at the time prior to T1, a potential detection circuit 4 detects it, sets an output signal phi1, to an 'H' level and sets an output signal phi2 to an 'L' level. At this time, the oscillation frequency of an output signal phi3, of an oscillation circuit 1 is set to f1. A drive circuit 2 drives a potential generation circuit 6 according to the frequency f1. On the other hand, since the substrate bias potential VSUB reaches the substrate bias potential VSU'B after the time of T1, the potential detection circuit 4 sets the phi1 to the 'L' level and the phi2 to the 'H' level. In this case, since the oscillation route of the oscillation circuit 1 is designed so as to be long as compared with that prior to the time of T1, the oscillation frequency of the output signal phi3, of the oscillation circuit 1 becomes f2 which is longer than f1. The number of operations per unit time of the potential oscillation circuit 3 becomes smaller than that prior to the time of T1. |
