Phase comparing apparatus

摘要

A lock detecting circuit of a phase locked loop, comprising a phase comparator for receiving a reference frequency signal and a signal being compared with the reference frequency signal, a charging/discharging circuit which is charge/discharge controlled responsive to the output of the phase comparator and either of the above described two signals, and a delay flip-flop responsive to the output of the charging/discharging circuit and in synchronism with the signal applied to the charging/discharging circuit for assuming one storing state for providing an output representative of the phase difference between the above described two signals.