| 摘要 |
PURPOSE:To obtain a phase detecting circuit which is small in the number of logic elements and suitable to a high speed action by adding an input signal and a signal obtained from a voltage control oscillating circuit to an exclusive OR circuit, phase-detecting them and obtaining the control signal of the voltage control generating circuit. CONSTITUTION:When the phase of an output pulse signal VCO(voltage control oscillating circuit) of a VCO3 and an input signal REF are mutually matched, the phase output signal of a duty 50% is generated at an EXOR 1. A control voltage is added from a control voltage generating circuit 4 to the VCO3 so that the VCO3 can be oscillated by the set reference oscillation frequency. The phase of the signal VCO is advanced for the input signal REF and at the time of becoming -45 deg., the phase output signal of a duty 75% is generated at the EXOR1. The control voltage corresponding to this is added from the control voltage generating circuit 4 to the VCO3 and the oscillation frequency of the VCO3 is controlled so as to go to the reference frequency. |
