Patent ID: 8519730

Claim:
A degradation detection system comprising: a first MOS transistor that is disposed between a first power supply and a second power supply, the second power supply including a lower potential than the first power supply; a first resistance unit that is connected in series with the first MOS transistor between the first power supply and the second power supply and includes slower degradation progress than degradation progress of the first MOS transistor; a first voltage output unit that outputs a voltage at a junction between the first MOS transistor and the first resistance unit; a degradation detection unit that detects degradation in the first MOS transistor according to the voltage output by the first voltage output unit; a first selection unit that, in a normal operation mode, selects a clock input and supplies a clock signal to the first MOS transistor via the first resistance unit, and in a measurement operation mode, selects the first power supply and supplies a constant voltage, which is supplied from the first power supply, to the first resistance unit: and wherein the degradation detection unit compares the voltage output by the first voltage output unit in a period while selecting the measurement operation mode with the voltage output by the first voltage output unit in a period different from the period while selecting the measurement operation mode, and detects the degradation in the first MOS transistor.