| 摘要 |
PROBLEM TO BE SOLVED: To enable the PLL device, which has a current output type charge pump circuit connected on the output side of a phase comparator and a non-lag/ lead type loop filter on the output side of the charge pump circuit, to actualize fast lock-up operation with very simple constitution. SOLUTION: In parallel to a resistance 16 of the loop filter 18, two diodes D1 and D2 are connected having the mutually opposite polarities. The diodes D1 and D2 are integrated on a PLL integrated circuit 20 together with the charge pump circuit 14, etc. A capacitor 15 for integration is charged with the output current I0 of the charge pump circuit 14 and the diode D1 or D2 is turned on when the absolute value |V0-V1| of the difference between the terminal voltage V0 across the capacitor 15 for integration and the terminal voltage V1 across a voltage holding capacitor 17 reaches the forward voltage drop Vth of the diodes D1 and D2 to charge the voltage holding capacitor 17 in a short time, so that variation needed as the terminal voltage V1 across the voltage holding capacitor 17 is obtained. |
