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This paper presents a low jitter adaptive-bandwidth charge pump PLL with an improved passive filter. With an adaptive bandwidth, the proposed PLL maintains optimal performance over its whole operating range. In order to improve the jitter performance of the PLL, matching technique is employed in the charge pump, and a voltage-to-voltage converter is used to achieve a low gain VCO. The novel circuit has been implemented in 0.35 mum CMOS process. Post simulation results show that the PLL can scale its loop dynamics proportional to the operating frequency and has good jitter performance within its operating range from 100 MHz to 1.1 GHz.