PLL FREQUENCY SYNTHESIZER

摘要

PROBLEM TO BE SOLVED: To provide a miniaturized and inexpensive switching PLL frequency synthesizer by reducing the number of parts to have a single low-pass filter(LPF) shared among plural voltage controlled oscillators (VCO). SOLUTION: The LPF 3 is connected to a charge pump output terminal 2 of a PLL-IC 1 and a control voltage terminal 5a of a VCO 4a, having an operation control terminal 6a and a control voltage terminal 5b of a VCO 4b having an operation control terminal 6b are connected in parallel to the LPF 3. By selectively switching the output current of a charge pump circuit 7 built in the PLL-IC 1 and the operation control terminals 6a and 6b of the VCO 4a and 4b, the PLL frequency synthesizer having different frequency bands can be provided.