Patent ID: 8102217

Claim:
An oscillator that creates a reference voltage based on a pulse signal corresponding to an oscillation output of an oscillation circuit, and that controls a maximum voltage level supplied to the oscillation circuit according to the reference voltage, the oscillator comprising: a control signal creating circuit that creates a first reference voltage control signal and a second reference voltage control signal based on the pulse signal; and a reference voltage generating circuit that creates a first reference voltage when receiving the first reference voltage control signal, and that creates a second reference voltage lower than the first reference voltage when receiving the second reference voltage control signal, wherein the control signal creating circuit creates the first reference voltage control signal when the pulse signal is in a first logic level, creates the second reference voltage control signal when the pulse signal is in a second logic level different from the first logic level, and prevents a transition from the second reference voltage control signal to the first reference voltage control signal when the pulse signal changes from the second logic level to the first logic level; and wherein the control signal creating circuit comprises: a current control circuit that controls an output current; a first capacitive element; a first gate that receives the pulse signal and outputs a signal so that the current control circuit and the first capacitive element control a change rate of a consecutively increasing or decreasing a level of the output current; and a second gate that outputs an output to produce the first and second reference voltage control signals according to an output signal of the first gate.