| 摘要 |
PURPOSE:To expand the variable range of the oscillation frequency of a voltage controlled oscillator by boosting a power supply voltage applied to a charge pump circuit in a frequency synthesizer. CONSTITUTION:After a frequency division output of the 2nd frequency divider 4 is boosted by a transformer 41, the boosted output is rectified by bridge diodes 53-56, stored in a capacitor 22 and used as a power supply for a charge pump circuit 6. When the phase locked loop is locked, the control voltage of the voltage controlled oscillator 1 is constant and a slight current flows to the charge circuit 6. Then the output current capacity of the transformer 41 of the boosting circuit 8 is made very small by employing the capacitor 22 and the volume of the transformer 41 is made small. Thus, the oscillating frequency of the voltage controlled oscillator 1 is in the range shown in a caption B and the variable range of the oscillation frequency is expanded, where VH is the power supply voltage of the boosted charge pump circuit 6. |
