| 摘要 |
PURPOSE:To reduce the number of components by constituting a loop filter of an operational amplifier, plural different resistors and capacitors, selecting the resistors and capacitors in response to the frequency of an input signal, and controlling a frequency division ratio of a frequency divider simultaneously. CONSTITUTION:A loop filter 3 consists of an operational amplifier 31, resistors and capacitors, and the frequency characteristic is varied by varying the resistors and capacitors. That is, plural different resistors R11-R1n are constituted to selectively switch and connect by a changeover switch circuit 32 to the operational amplifier 31 and similarly series circuits each comprising plural resistors R21-R2m and capacitors C1-Cm are constituted to selectively switch and connect by using a changeover switch circuit 33. Then the resistance and the capacitance to the operational amplifier 31 are varied by the switching resulting in varying the frequency characteristic. Thus, the number of components is reduced. |
