Patent ID: 7042298

Claim:
An oscillator circuit, in which a feedback resistor, an inverter, and a plurality of tri-state inverters are connected in parallel across a resonator and oscillation capability of the resonator is controlled by switching the number of driven tri-state inverters out of the plurality of tri-state inverters, the oscillator circuit comprising four inverters fed with oscillation output from the resonator, wherein each of the four inverters has a different threshold value relative to the oscillation output from the resonator, two of the four inverters have threshold values at an allowable upper limit voltage level for obtaining stable oscillation from the resonator, the other two inverters have threshold values at an allowable lower limit voltage level for obtaining stable oscillation from the resonator, and the number of driven tri-state inverters out of the plurality of tri-state inverters is switched based on an output value of each of the inverters when the oscillation output from the resonator is inputted, the plurality of tri-state inverters are switched by means of a difference of threshold values of the inverters controlling the amplitude of the oscillation circuit wherein each of the inverters receives a pre-set input threshold signal.