PURPOSE: To attain low-voltage operation and to improve oscillating frequency characteristics by providing an oscillator making oscillation and giving an output and a boosting circuit boosting a signal voltage generated from the oscillator thereby extending a permissible power voltage.

CONSTITUTION: A voltage VD is fed to a power terminal 20 via a switch 14 and a CR generator 2 starts generating a clock pulse. When the clock pulse is received by a latch 15, the output of the latch is inverted, the switches 12, 14 are turned off and switches 11, 13 are turned on and the state is held respectively. While a transmission signal of an inverter 16 is at a zero voltage, the switch 11 is turned on, the switch 12 is turned off and a diode D is turned on and the voltage VD is charged. While the signal of the inverter 16 is positive, the switch 11 is turned off, the switch 12 is turned on and the charging voltage of the capacitors C2, C1 is charged by a voltage being the sum of the voltage VD and the voltage sent from the inverter 16. Thus, the boosted voltage is supplied to the CR oscillator 2 as the power voltage.