| 摘要 |
PURPOSE:To prevent out of synchronization of a phase synchronizing circuit at changeover by constituting a resistive element for an integration circuit with a source-drain resistance of a field effect transistor(TR) and controlling the said field effect TR by a control signal so as to vary the resistance. CONSTITUTION:A noise band switching control signal is inputted from a terminal Z1 to vary a gate voltage of a field effect TR 1 and the drain-source resistance of the field effect TR 1 is RS1 at On state and RL1 at off state. When an input terminal Z1 for a band switching control signal is at an off-level, the loop locking range and noise band are both widened and they are made narrow when the terminal Z1 is at on-state. The drain-source resistance is changed by the control of a gate voltage of the field effect TR 1 with a band switching control signal and the noise band is switched without causing a change of a voltage across the capacitor C1. Thus, a phase synchronizing circuit is switched without causing out of synchronism. |
