a self - tuning technique for integrated continuous - time filters . the present invention provides a method and apparatus to compensate for post - fabrication or in - operation discrepancies between desired and measured filter characteristics due to variability of the ic fabrication process or due to drift caused by changing conditions such as voltage , temperature . the present invention requires minimal overhead in power and area requirements . furthermore , the filter being tuned is used to process signals , unlike in the prior art where a similar but separate filter or oscillator is used to tune the bias values for both circuits . better tuning accuracy is thus obtained in the present invention . the circuit is designed to initiate a self - tuning cycle at power - up or during operation after power - up . tuning is achieved by injecting a reference signal , and monitoring the phase of the filter output with respect to the phase of the reference signal . the self - tuning circuit then provides a signal to a trim dac , which applies the appropriate correction signal .