Multiband transceivers are very popular now-a-days. As a key component in the system, the broadband VCO is a hot research topic. This paper presents a broadband Logic inductor Capacitor Voltage Controlled Oscillator (LC-VCO) with an Adaptive Frequency Calibration (AFC) circuit. The VCO uses a 5-bit differential switched-capacitor array for extending the tuning range. Two couples of AMOS varactors are employed to linearize the VCO tuning gain. An AFC circuit is utilized to automatically select the optimal sub-band for the VCO by binary search algorithm.