PURPOSE: To enable the perfect removal of an AC component by a way rich in generality, by extracting only an AC conponent from an analogue input signal, and adding the extracted signal to the analogue input signal while reversing the polarity thereof.

CONSTITUTION: For example, a DC breaker circuit 1 is constituted of a capacitor. By this constitution, an analogue signal B only comprising an AC component Vp is outputted from the DC breaker circuit 1. This analogue signal B is reversed in its polarity, for example, in a polarity reversing circuit 2 to be converted to an analogue signal C which is, in turn, supplied to an adder 3. To the other addition input of the adder 3, an analogue signal A containing a DC component Vd and an AC component Vp is inputted and predetermined operation is performed. As a result, an analogue signal only comprising the DC component Vd is outputted. In this case, because the capacitor of the circuit 1 removes only a DC component, it is unnecessary to strictly select constant corresponding to the frequency of the AC component. Therefore, the AC component can be perfectly removed by a way rich in genelarity.