FREQUENCY SYNTHESIZER

摘要

A phase difference detecting circuit (3) comprises: a sync detecting circuit (21) that detects an establishment of phase sync from phase difference signals (D, U) generated by a D-type flip-flop (13); a switch (22) that, if the sync detecting circuit (21) detects no establishment of phase sync, then outputs a control voltage (Vt1), which is generated by a responsive-to-current-output loop filter (15), to a voltage controlled oscillator (4) and that, if the sync detecting circuit (21) detects the establishment of phase sync, then outputs a control voltage (Vt2), which is generated by a responsive-to-voltage-output loop filter (20), to the voltage controlled oscillator (4); and so on.