| 摘要 |
PROBLEM TO BE SOLVED: To operate, at a low cost, a charge amplifier for converting electric charge generated in a piezoelectric pressure sensor, with one end grounded, into a voltage signal. SOLUTION: In this charge amplifier 1, a positive-side power input terminal of a operational amplifier 5 is connected to a positive power source (+5 V) while a negative-side power input terminal thereof is grounded, thus powering the operational amplifier 5 by a single power source. Further, an offset voltage lower than the positive source voltage and higher than the ground potential is applied to a non-inverted input terminal of the operational amplifier 5. This makes it possible to convert a change in pressure either on the positive or negative side into a voltage signal centering around the offset voltage even if the operational amplifier 5 is powered only by the single source. That is to say, two power sources are not required and therefore the cost can be suppressed. |
