| 摘要 |
PROBLEM TO BE SOLVED: To exclude influence of in-phase noise Vn in an input signal of a differential amplifier while a consumption current of a VAG power source circuit 12 which generates almost one-half voltage of a power source voltage VDD is restrained. SOLUTION: Resistors R5, R6 output a voltage Vnc of a mean value of voltages Vim, Vip at an inverting input end im and a non-inverting input end ip of an operating amplifier 3, from the voltages Vim, Vip. In a current supply circuit 4, transistors M7, M1 which are connected to the ground potential are turned on when voltage Vnc is increased, and the voltages Vim, Vip are pulled down. When the voltage Vnc is decreased, transistors M8, M9 which are connected with the power source voltage VDD are turned on, and the voltages Vim, Vip are pulled up.
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