Patent ID: 7369006
Filing Date: 2008-05-06
Classification: H03B,H03L

Abstract:
1. An applied voltage control circuit for a voltage controlled oscillation circuit comprising: a first transmission gate inserted between a control input terminal of the voltage controlled oscillation circuit and a power-supply terminal; a second transmission gate inserted between the control input terminal of the voltage controlled oscillation circuit and a voltage control terminal; and an NPN transistor for switching an applied voltage inserted between a connection point of the power-supply terminal and the first transmission gate, and a ground terminal, and controlled by a control signal applied to a general purpose terminal externally controlled, wherein a collector of the NPN transistor is connected to a gate of an NMOS transistor of the first transmission gate and a gate of a PMOS transistor of the second transmission gate, and further connected to a gate of a PMOS transistor of the first transmission gate and a gate of an NMOS transistor of the second transmission gate via an inverter, the NPN transistor is disconnected when a power supply is turned on so that the first transmission gate is conducted and the second transmission gate is disconnected, and a power-supply voltage of the power-supply terminal is applied to the control input terminal of the voltage controlled oscillation circuit via the first transmission gate in the conducted state, and the NPN transistor is switched to the conducted state by the control signal applied to the general purpose terminal after oscillation of the voltage controlled oscillation circuit is stabilized so that the first transmission gate is switched to the disconnected state and the second transmission gate is switched to the conducted state, and a voltage of the voltage control terminal is applied to the control input terminal of the voltage controlled oscillation circuit via the second transmission gate in the conducted state.