| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an amplifier that can change the amplification factor without being dependent on a sensor voltage.SOLUTION: An amplifier has a differential amplifying circuit (10), an input resistance unit (20) and a feedback resistance unit (30). At least one of the feedback resistance unit and the input resistance unit has plural basic resistors (50a to 50c) which are connected to wires provided to themselves in series, and variable resistance units (60a to 60c) which are provided at the midpoint between any two of the plural basic resistors. The variable resistance unit has resistors (64a to 64c, 65a to 65c) and switches (66a to 66c, 67a to 67c) which are successively connected in series from the midpoint of the two basic resistors to the reference potential, and a controller (63) for controlling the operation of the switches. The switch is MOSFET, and the source electrode or drain electrode of the switch is connected to the reference potential.</p> |
