1. An apparatus comprising: an adaptive continuous-time filter including a first array of elements and a control input configured to receive an output word that generates a filter response to account for effects of semiconductor process variation in the first array of elements; and a controller configured to generate a digital word responsive to a time constant, to compare a select bit of the digital word to a corresponding reference word to generate a control bit, to apply the control bit to an adjustable element to modify the time constant, and to provide the output word to the adaptive continuous-time filter.