| 摘要 |
PURPOSE:To more precisely cope with the lock state by applying a phase lock signal from a phase comparator to a terminal, which controls the value of the constant current of a charge pump driven with a constant current, through an integrator. CONSTITUTION:A phase lock signal 10 of a phase comparator 3 is obtained as a pulse signal whose pulse width is changed in accordance with the lock state of a PLL circuit. This signal is inputted to an integrator 15 through a buffer amplifier 14, and a part of the output of the integrator 15 is inverted by a polarity converting part 16 to obtain a pair of outputs (d) and (e). They are applied as the control input of a current variable charge pump to continuously change the driving current of the current variable charge pump 11, thus changing the loop characteristic of PLL. |
