| 摘要 |
PURPOSE:To make a phase comparison definite by providing a charge pump circuit which performs constant-current drive corresponding to the output signal of a phase comparator circuit. CONSTITUTION:The gate electrode of transistor Tr 45 is connected to the phase lagging pulse output terminal of phase comparator 2, and the gate electrode of Tr 46 is to the phase leading pulse output terminal. Both Tr 41 and Tr 43 are coupled together via resistance 42 and operate as resistance elements. Adjusting resistance value R controls a current flowing through Trs 41 and 43, so that gate voltages of Trs 44 and 47 can be fixed. On the arrival of a phase leading pulse, Tr 46 is ON and Tr 45 is OFF to start discharge. Since the gate and source voltages of Tr 47 are held below power voltage VDD at this time, the operation is hardly influenced by the drain and dource voltages of Tr 47. On the other hand, adjusting resistance 42 to such a state causes constant-current drive. |
