PURPOSE: To independently and stably amplify plural kinds of signals by setting an input terminal of an operational amplifier to which a first and a second signals are inputted to a virtual ground level at the time of bringing these first and second signals to inversion amplification.

CONSTITUTION: When a first signal Sh and a second signal Sv are inputted to an input terminal P1 of an operational amplifying circuit OP, as for a first signal Sh, its amplitude is varied between for instance, a ground level being a reference level or its approximate level and a first level being larger than this reference level. On the other hand, as for a second signal Sv, its amplitude is varied between for instance, the reference level and a second level being smaller than this reference level. By setting the input terminal P1 to which such a first and a second signals Sh, Sv are inputted to a virtual ground level, both the signals can be amplified stably. In such a way, plural kinds of signals can be amplified independently and stably.