Patent ID: 8248099

Claim:
A semiconductor integrated circuit, comprising: an internal circuit; and a measuring circuit, wherein the internal circuit and the measuring circuit are formed in a semiconductor chip, wherein the internal circuit comprises a low-threshold-voltage MOS transistor and a high-threshold-voltage MOS transistor, and the degree of threshold voltage variation of the low-threshold-voltage MOS transistor is larger than the degree of threshold voltage variation of the high-threshold-voltage MOS transistor, wherein the measuring circuit detects which one of fast, typical, and slow states is taken by both the low-threshold-voltage MOS transistor and the high-threshold-voltage MOS transistor in the internal circuit, wherein a level of power supply voltage to be fed to the internal circuit is set up in response to result data detected by the measuring circuit, wherein, when the result data detected indicates the fast state, the power supply voltage is set to a lower power supply voltage level corresponding to a small variation gradient in terms of the rate of voltage change with respect to speed variation, wherein, when the result data detected indicates the typical state, the power supply voltage is set to an intermediate power supply voltage level, and wherein, when the result data detected indicates the slow state, the power supply voltage is set to a higher power supply voltage level corresponding to a large variation gradient in terms of the rate of voltage change with respect to speed variation.