PURPOSE: To decrease number of elements by using input variables to a node equation for an input, output and an integration device of the node equation and erasing other variables and modifying the equation so as to obtain a signal flow graph.

CONSTITUTION: An equivalent conversion circuit including a current control current source is obtained from an original circuit comprising a high-pass LC filter. Then the node equation is obtained from the circuit. Then the input variables of the input, output and the integration device of the node equation for the node equation are used, other variables are erased, the equation is modified to obtain the signal flow graph. Then a high-pass switched capacitor filter (SCF) is obtained by using switched capacitors X1∼X9 and operational amplifiers A1∼A3 from the signal flow graph. Through the constitution above, the leapfrog high-pass SCF with a few number of sampling switches S and switched capacitors is constituted.