| 摘要 |
PURPOSE:To switch easily the polarity of loop of a PLL by providing a switch circuit inverting/noninverting an input polarity voltage to a phase detector to keep stability without incurring increase in number of components. CONSTITUTION:An integrated circuit 110 for PLL has a switch circuit 30 at the pre-stage of a phase comparator in order to switch the polarity of a signal to a phase comparator 6. It is possible to replace a reference frequency and a variable frequency dividing output when viewed from a phase detector 6 side by controlling an input 31 of the switch circuit 30, thereby inverting the polarity of loop. Further, an output of the integrated circuit 110 is supplied to a low-pass filter and its output controls an oscillating frequency of a voltage controlled oscillator and a part of the oscillating signal is supplied as an input to the integrated circuit 110. Further, a crystal oscillator is connected to the input of an oscillator 2 for reference frequency. |
