Disclosed is an oscillator including: a digital to analog converter configured to convert a received control code into an analog voltage and output the converted analog voltage; a mirror circuit configured to adjust a current of a common output node to which the analog voltage is applied; and a periodic signal output circuit configured to output a periodic signal having a frequency according to the analog voltage, in which the digital to analog converter, the mirror circuit, and the periodic signal output circuit are implemented with tri-state inverters.