A low-power high-output-efficiency bipolar Colpitts VCO using base inductive feedback and Q-factor enhancement for analog signal acquisition

Abstract

A low-power Colpitts VCO with high output efficiency that uses base inductive feedback and Q-factor enhancement techniques is proposed in this paper. The base inductive feedback technique employs an inductor at the base of the bipolar transistor to generate a feedback enhancement effect and reduce the start-up current. The Q-factor enhancement technique adopts a capacitor voltage divider at the output of the Colpitts VCO to improve the DC-to-RF efficiency. The mechanisms are theoretically analyzed, and then a 433 MHz Colpitts VCO is designed to verify the scheme. Its DC consumption is as low as 270 µW while the operating frequency is 433 MHz. Finally, the Colpitts VCO is applied in a wireless neural signal recording system and works well. Thus, the presented VCO is suitable for analog signal acquisition system in the extremely power-constrained wireless scenarios.