Semiconductor integrated circuit including a filter with adjustable cut-off frequency

摘要

A semiconductor integrated circuit includes a filter and a time-constant detecting circuit. The filter includes resistance elements; capacitance elements, each of which consists of a capacitance-value switching circuit that can vary the capacitance of the capacitance elements and operational amplifiers. The time-constant detecting circuit detects the time constant of the capacitance element and resistance element, which are formed independently of the capacitance elements and resistance elements of the filter. The semiconductor integrated circuit varies the capacitance of the capacitance element in response to the detected time constant to prevent a reduction in the yield by adjusting the cut-off frequency of the filter in spite of variations in manufacturing the resistance elements and capacitance elements of the filter.