Method and device for reducing sensitivity of ratio converter type circuit to interference signal and noise

PURPOSE: To obtain a method and device for reducing sensitivity of a ratio converter type circuit to disturbing signals and noise. CONSTITUTION: A ratio converter generates an output signal COUT which is proportional to an external detecting signal AIN and an external reference signal VREF (EXT) upon receiving the signals AIN and VREF (EXT). Electromagnetic interference signals and noise coupled with the signals AIN and VREF (EXT) are effectively removed when the signals AIN and VREF (EXT) are converted into digital signals. The digitized detecting signal is filtrated through a low-pass filter 22 and the digitized reference signal is also filtrated through another low-pass filter 30. A divider circuit 24 generates an output signal by dividing the filtrated digital detecting signal by the filtrated digital reference signal.