Frequency synthesizer device and mobile radio device using the same

摘要

In a frequency synthesizer device in which a frequency-division ratio control circuit 6 and other circuits are integrated on the same semiconductor substrate, a power supply 8 for supplying a power to the frequency- division ratio control circuit 6 is provided separately from a power supply 7 for supplying a power to other circuits. A power supply voltage supplied from the power supply 8 to the frequency-division ratio control circuit 6 is set lower than a power supply voltage supplied to other circuits. The noise generated by the frequency-division ratio control circuit 6 can be reduced by setting the power supply voltage lower, and also C/N degradation can be reduced. Since the noises can be suppressed even if the frequency is increased, a lock-up time can be reduced and the lower power consumption can be attained.