VOLTAGE CONTROL OSCILLATION CIRCUIT, PLL CIRCUIT AND TUNER

摘要

PROBLEM TO BE SOLVED: To provide a voltage control oscillation circuit in which a field effect transistor (FET) is used in a negative conductance part for continuing an oscillation operation, and phase noise of an output signal due to modulation of a variable capacitor by low frequency noise such as flicker noise due to channel current of FET can be suppressed and to provide a PLL circuit and a tuner. SOLUTION: A control voltage terminal 107 is connected between the variable capacitors 101 and 102. DC potential is given between fixed capacitors 103 and 104 which are connected to the variable capacitors 101 and 102 in series and the variable capacitors 101 and 102 through an element (DC feeding element) 105 constituting a high pass filter (HPF) with the fixed capacitor 103. Thus, modulation of the variable capacitor 101 and the like by low frequency noise is suppressed. COPYRIGHT: (C)2005,JPO&NCIPI