| 摘要 |
PURPOSE:To apply stable voltage controlled oscillation over a wide range even when a power voltage of a PLL is a low voltage by providing a boosting means between a phase comparison means and a voltage controlled oscillation means so as to apply a large DC voltage to the voltage controlled oscillation means. CONSTITUTION:An output voltage e1 of a tank circuit 231 is boosted to a large voltage e2 by a boosting means being a transformer 233, rectified by a rectifier circuit 235, its rectified signal 237 is smoothed through a low-pass filter 239 to obtain a DC voltage signal 221. A voltage controlled oscillator VCO 223 consists of, e.g., a varactor diode and its capacitance is controlled variably in response to a DC voltage of the DC voltage signal 221. Thus, an oscillated output frequency fout of the output signal 225 of the VCO 223 is controlled. Then even when a low voltage supply is used for the PLL power supply, the DC control voltage 221 sufficiently for the voltage controlled oscillation of the VCO 223 properly over a wide range is obtained.
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