PURPOSE: To reduce the number of memories, to simplify the configuration of a control circuit and to reduce the size of a crystal oscillator and its power consumption by storing data required for the setting of control voltage in a memory as one group.
CONSTITUTION: Temperature detection data, amplification degree setting data and offset voltage data are stored in a memory 36 as one control voltage setting group up to a maximum of eight groups. When temperature detected by a temperature sensor 30 is transmitted to a temperature detecting part 32, temperature detection data in eight control voltage groups stored in the memory 36 are successively supplied to the temperature detecting part 32 as analog signals through a D/A conversion part 39 and compared with the input signal from the sensor 30 and adaptive amplification degree setting data and offset voltage data are selected and supplied to an amplification part 31 and a D/A conversion part 37. Thus variation in the oscillation frequency of a voltage controlled oscillator 42 due to temperature variation can be suppressed based upon these supplied data.
MOCHIDA YOSHIHISA
MIZUKOSHI TAKASHI
MAEDA CHIKAO
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