| 摘要 |
<P>PROBLEM TO BE SOLVED: To incorporate a low-pass filter in a chip by miniaturizing a circuit element constituting a low-pass filter in a PLL circuit, especially reducing the capacitance. <P>SOLUTION: An active filter employed in a PLL circuit having two charge pump circuits at the post-stage of a phase comparator comprises a first circuit element connected between the output of one charge pump circuit and the earth, a second circuit element connected between the output of the other charge pump circuit and the earth, and a voltage adder for adding the voltage across the first circuit element and the voltage across the second circuit element. <P>COPYRIGHT: (C)2007,JPO&INPIT |
