| 摘要 |
PROBLEM TO BE SOLVED: To provide a crystal oscillator which can keep the temperature of a crystal resonator to be a desired value and is high in frequency stability by preventing the hunting of a heater current without reducing the control gain of a heater current control circuit and without causing the increase of the size of the oscillator. SOLUTION: The oscillator is provided with electric heaters 11 and 12 for heating the crystal resonator, a temperature sensor 20 for detecting the temperature of the heaters 11 and 12, and a heater current control circuit 30 for controlling the heater current so as to keep the temperatures of the heaters 11 and 12 to be prescribed values in accordance with the output of the sensor 20. The circuit 30 is provided with a switching element 31 for turning on/off the heater current and an arithmetic amplifier 32 for operating the element 31 in accordance with a difference value between a feedback voltage corresponding to the heater current and an input voltage corresponding to the output of the sensor 20. An integration circuit 39 having a time constantτ(=R5×C2) longer than a time T required to sense the temperature variation of the heaters 11 and 12 by a temperature sensor 20 and consisting of a resistor 40 and a capacitor 41 is provided in the middle of a circuit for feeding back the feedback voltage to the amplifier 32.
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