The feedback system includes an input signal generation circuit configured to output an input signal having a level corresponding to a code signal inputted thereto and a lock signal generation circuit configured to output the code signal for controlling a level of the input signal using two reference signals, to generate count data acquired by counting time from when the level of the input signal reaches between levels of the two reference signals to when the level of the input signal becomes higher or lower than the level of any one of the two reference signals, and to output a lock signal for fixing the level of the input signal after time corresponding to a rounded value of a quotient of the count data divided by 2.