| 摘要 |
PURPOSE:To set the oscillation frequency characteristic to an externally applied voltage optionally by digital-coding an external applied voltage, converting the result into an analog signal so as to set the A/D conversion rate and the D/A conversion rate. CONSTITUTION:An external applied voltage is once converted into a digital code (hereinafter referred to as DC) by an A/D converter 3 and its output DC is fed to a memory circuit 4. A voltage control DC corresponding to the DC being an address signal is stored in advance in the circuit to control the change in the oscillated frequency depending on the externally applied voltage. In varying the externally applied voltage, the address signal is also changed and the voltage controlled DC is read from the circuit 4 accordingly, converted into an analog signal by an A/D converter 5 to control the static capacitance of the varactor element 2. The oscillation frequency of the piezoelectric oscillation circuit comprising a piezoelectric resonator 1, a transistor Q, resistors R1-R7 and capacitors C1-C4 are controlled by the capacitance value. |
