Patent ID: 7579917

Claim:
A crystal oscillator formed by connecting an output terminal of an oscillator having a quartz vibrator to an oscillation output terminal through a buffer circuit, wherein a switch is connected to a part of the buffer circuit which changes oscillation characteristics, the crystal oscillator comprising a shift control unit for controlling the turning on/off of the switch, wherein an output terminal of the oscillator having the quartz vibrator is connected to an input terminal of an inverter connected to a first resistor and one terminal of a second resistor, wherein the other terminal of the first resistor is connected to one terminal of a first capacitor and an input terminal of a first transistor, wherein the other terminal of the first capacitor is connected to one terminal of a first switch, wherein the other terminal of the first switch is grounded, wherein the other terminal of the second resistor is connected to one terminal of a second capacitor and an input terminal of a second transistor, wherein the other terminal of the second capacitor is connected to one terminal of a second switch, wherein the other terminal of the second switch is grounded, wherein an output terminal of the first transistor and an output terminal of the second transistor are connected to the oscillation output terminal, and wherein the first switch and the second switch are controlled by the shift control unit.