Cut-off frequency correction circuit for filters

A cut-off frequency correction circuit for filters, inputting with a step function increased from a first voltage to a second voltage, comprises a linear non-active filter, for integrating the step function to get a third voltage; a first comparator, outputting high frequency signals when the third voltage is higher than a first reference voltage; a second comparator, outputting high frequency signals in a first time interval from the time that the second voltage is applied, to the time that the first comparator outputs high frequency signals; a counter, for counting a number of reference clocks inputted in the first time interval; a digital block, for calculating a rate of time constant of filter according to the number of reference clocks, and generating a correction code; and a filter, for correcting a cut-off frequency according to the correction code. The correction circuit is capable of speeding up the adjustment of the cut-off frequency.