Abstract: An output correction apparatus that corrects offset drift of a cylinder internal pressure sensor, and a cylinder internal pressure detection apparatus that accurately detects cylinder internal pressure of an internal combustion engine through use of the output correction apparatus. The cylinder internal pressure detection apparatus includes a detection circuit section which detects a change in the resistance of a piezoresistor element as an electrical signal; an amplification circuit section which amplifies and outputs the electrical signal (output value); and a correction circuit section which corrects the output value. The correction circuit section includes a reset control section which resets the output value of the amplification circuit section to a reference value, and a reset timing detection section which determines a timing of the resetting.

Abstract: An object of the present invention is to provide a charge amplifier which can be operated at low cost so that electric charge generated in a piezoelectric pressure sensor having one end grounded is converted into a voltage signal. In the charge amplifier (1) according to an embodiment of the present invention, a plus side power source input terminal of an operational amplifier (5) is connected to a plus power source (+5 V) while a minus side power source input terminal of the operational amplifier (5) is grounded, so that the operational amplifier (5) is supplied with a single power source. Further, an offset voltage lower than the plus power source voltage but higher than the ground potential is applied to a non-inverted input terminal of the operational amplifier (5). Accordingly, change of pressure in both positive and negative directions can be converted into a voltage signal with the offset voltage as its center though the operational amplifier (5) is driven by a single power source.