| 摘要 |
PROBLEM TO BE SOLVED: To surely oscillate even a the prescribed oscillation start voltage and to decrease the noises in a normal oscillation operating mode by controlling the gain of an amplifier circuit at high and low levels in the ranges where the power voltage of low and high levels are supplied to the amplifier circuit, respectively. SOLUTION: In a range where the power voltage is lower than the threshold voltage, the thresholds of a P-MOS transistor TR 1 and an N-MOS TR 2 have low levels and the gain of an amplifier circuit consisting of an inverter and a feedback resistance 4 is kept at a high level. When the power voltage is raised up to the prescribed oscillation start voltage, an oscillation circuit starts easily its oscillation. In a range where the power voltage is higher than the threshold voltage, the TR 1 and TR 2 have high thresholds and the gain of the circuit 4 is lowered. When the power voltage is raised up to a level of a normal mode, the driving capability of the amplifier circuit is suppressed and accordingly the driving capability of the oscillation circuit is also suppressed to decrease the noises.
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