| 摘要 |
PURPOSE:To eliminate influence due to the change in the lapse of time of a volume or a variable capacitor and to improve stability, by providing an arithmetic circuit which calculates an adjusting signal at the front of a D/A converter which converts a temperature compensating signal. CONSTITUTION:A bit of temperature information from a temperature detecting element is inputted from a terminal 1, and it is converted to a digital signal at an A/D converter 2. A temperature data converted to the digital signal is inputted to a first memory circuit 3 where the bit of temperature information of a crystal oscillator for temperature is stored in a ROM, and the compensating signal is outputted. The compensating signal is inputted to the arithmetic circuit 4. The arithmetic circuit 4 performs addition or subtraction, and calculates it with a data signal for fine adjustment from an adjusting circuit 5. The output of the arithmetic circuit 4 is converted to an analog signal at the D/A converter 7, and is outputted from a terminal 8, and is inputted to a variable capacitance diode, etc., then, the frequency of the crystal oscillator can be compensated.
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