| 摘要 |
PROBLEM TO BE SOLVED: To realize highly accurate temperature compensation by compensating for the linearity of f-V characteristics of a varactor diode constituting a temperature compensated crystal oscillator, thereby keeping the linearity of output oscillation frequency for the control voltage as a high accuracy VCO. SOLUTION: A compensation voltage generated from a temperature compensated voltage generating circuit 11, comprising a primary voltage generating circuit 9 and a tertiary voltage generating circuit 10, is applied to a varactor diode 5 in order to vary the equivalent capacitance, and a frequency variation in the oscillation loop caused by variation of the equivalent capacitance is offset the temperature characteristics of frequency of an AT cut crystal oscillator 6. In the temperature compensated crystal oscillator of such an arrangement, the primary voltage generating circuit 9 is provided with a gain control amplifier 18a for controlling the output voltage thereof, the tertiary voltage generating circuit 10 is provided with a gain control amplifier 18b for controlling the output voltage thereof, and the gain of the gain control amplifiers 18a and 18b is controlled by the output voltage level of an AFC circuit 13.
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