A frequency variable oscillator is provided to vary the oscillation frequency according to the variable of current by converting the voltage of the input signal into current. An oscillator(100) comprises a voltage-to-current conversion circuit(110) and an oscillator circuit(120). The voltage-to-current conversion circuit comprises a voltage down(111) and a voltage current conversion part(112) and a current controller(113). The voltage down comprises a comparator(111a) and a voltage range regulator(111b). The voltage current conversion part comprises a voltage-current converter(112a) and a current gain regulator(112b). The current controller comprises a current operator(113a) and the first and second current multipliers(113b,113c). An oscillator circuit comprises the charge and discharge section(121) and a signal generator(122). The signal generator comprises the first and the second comparator(C1,C2) and the RS latch(La).
