PURPOSE: To realize a transducer having high stability and high accuracy, by executing addition and subtraction of each DC voltage being proportional to a power of a phase difference of 2 AC inputs, and reference voltage, so that DC voltage being proportional to a power-factor can be outputted.

CONSTITUTION: Each AC input of a phase difference () of a terminal 1 and 2 becomes sqaure wave voltage by a comparator 11 and 12, exclusive OR is taken by a gate 13, and it becomes voltage 53 of a duty ratio being proportional to the phase difference (). The voltage 53 is applied to a control terminal of switches S1, S2, and S1 outputs a peak value Ez by making reference voltage Ez pass through when the voltage 53 is high, and by making it pass through a filter A1, DC voltage E21 being proportional to the phase difference () is obtained. The voltage E21 is supplied to S2 and A2, and in the same way, as to the phase difference (), voltage E22 being proportional to 2 is obtained. Voltage E21, E22 and Ez is subjected to addition and subtraction in the decided ratio by an adding and subtracting circuit AD, and DC voltage E25 being proportional to a power-factor of an input is outputted.