A wide-band voltage controlled oscillator includes a cross-connected transistors for providing a stable oscillating signal, an inductor unit for providing an inductance for determining a resonance frequency, a varactor bank including a plurality of switchable variable-capacitance elements parallely connected to the inductor unit and having a varactor capacitance varying with the first switching signal and a tuning voltage, a subsection capacitor bank including a plurality of switchable capacitor elements parallely connected to the inductor unit and having predetermined capacitances for grouping frequency sections, and a binary-weighted capacitor bank including a plurality of binary-weighted capacitor arrays parallely connected to the inductor unit and a bank selector for selecting one of the binary-weighted capacitor arrays, wherein each binary-weighted capacitor arrays includes a plurality of parallely connected switchable capacitor elements selectively switched on by a third switching signal to determine a variable weighted capacitance of the tunable binary-weighted capacitor bank.