FREQUENCY ADJUSTING CIRCUIT

PURPOSE:To adjust the initial deviation of the frequency with a resistance value of a resistance voltage division circuit of a regulating voltage generating circuit by connecting a capacitor and a varactor diode in series between an output or an input an inverter or ground and connecting a regulating voltage generating means by a resistance voltage division to a connection section of the capacitor and the varactor diode. CONSTITUTION:The oscillated frequency of a crystal oscillation circuit 1 depends on a series capacitance Ct comprising a static capacitance Cd of a varactor diode 11 and a static capacitance Cc of a capacitor 10. The static capacitnace Cd of the varactor diode 11 is proportional to (V) in the case of grade junction (diffusion junction) and to (3V) in the case of step junction (alloy junction). Thus, the oscillated frequency is varied by varying a reverse bias voltage of the varactor diode 11 and a voltage regulating voltage Va) to the objective specified frequency is supplied from a regulating voltage generating means 12 to adjust the specified frequency. The regulating voltage Va is obtained without packaging the resistors 13, 14 at the predetermined frequency, and decided by the resistors 13, 14 with the voltage division ratio of the regulating voltage Va are packaged or the resistor 13 or 14 is trimmed.