Voltage controlled oscillator

The present invention discloses a technology that enables to generate a signal of a constant cycle in response to changes in input power to the voltage-controlled oscillator which relates to a voltage controlled oscillator, in particular, used in the self-refresh operation of the DRAM. To this end, the present invention is to use the self-refresh operation during start-up circuit for performing a refresh operation at predetermined cycles in the dynamic random access memory, regardless of the variation of the input power source providing a constant bias current to the oscillator unit and to enable the operation of the stable DRAM .